Modify tumbler defaults to improve privacy

This is part of the 2/2019 Plan to improve the privacy of JoinMarket's
tumbler script:
https://gist.github.com/chris-belcher/7e92810f07328fdfdef2ce444aad0968

Also text for the eventual release notes is provided

docs/release-notes/release-notes-tumbler-improve.md

@@ -0,0 +1,20 @@
+copypaste this into "release-notes" when the time comes to make a new release, then delete this file
+
+Notable changes
+===============
+
+### Tumbler privacy improvements
+
+The tumbler algorithm has been improved with the aim to increase privacy. This affects the `tumbler.py` script and `joinmarket-qt.py` GUI.
+
+* At the start of the run, tumbler will now fully spend all mixdepths with coinjoin with no change address (also known as a sweep transaction) back to its own internal wallet. After these initial sweeps are done tumbler will continue with the already-existing algorithm of sending coinjoins with randomly-generated amounts.
+
+* Tumbler will now occasionally send a round number of bitcoins, for example `0.20000000` or `0.15000000` instead of `0.24159873`. The default probability of this happening is 25% per coinjoin.
+
+* The default wait time between coinjoins is increased from 30 minutes to 60 minutes.
+
+* The default number of coinjoin counterparties is increased from 6 to 9.
+
+* The default number of coinjoins per mixdepth is decreased from 4 to 2.
+
+For a full discription and reasoning behind the changes see: [Plan to improve the privacy of JoinMarket's tumbler script](https://gist.github.com/chris-belcher/7e92810f07328fdfdef2ce444aad0968)

jmclient/jmclient/configure.py

@@ -250,7 +250,7 @@ tx_broadcast = self
 # amount of makers which we are content with for the coinjoin to
 # succceed. Less makers means that the whole process will restart
 # after a timeout.
-minimum_makers = 2
+minimum_makers = 4
 
 ##############################
 #THE FOLLOWING SETTINGS ARE REQUIRED TO DEFEND AGAINST SNOOPERS.

scripts/cli_options.py

@@ -269,9 +269,9 @@ def get_tumbler_parser():
             action='store',
             dest='makercountrange',
             help=
-            'Input the mean and spread of number of makers to use. e.g. 6 1 will be a normal distribution '
-            'with mean 6 and standard deviation 1 inclusive, default=6 1 (floats are also OK)',
-            default=(6, 1))
+            'Input the mean and spread of number of makers to use. e.g. 9 1 will be a normal distribution '
+            'with mean 9 and standard deviation 1 inclusive, default=9 1 (floats are also OK)',
+            default=(9, 1))
     parser.add_option(
             '--minmakercount',
             type='int',
@@ -292,17 +292,17 @@ def get_tumbler_parser():
             type='float',
             nargs=2,
             dest='txcountparams',
-            default=(4, 1),
+            default=(2, 1),
             help=
             'The number of transactions to take coins from one mixing depth to the next, it is'
             ' randomly chosen following a normal distribution. Should be similar to --addrask. '
-            'This option controls the parameters of the normal distribution curve. (mean, standard deviation). default=4 1')
+            'This option controls the parameters of the normal distribution curve. (mean, standard deviation). default=2 1')
     parser.add_option(
             '--mintxcount',
             type='int',
             dest='mintxcount',
-            default=1,
-            help='The minimum transaction count per mixing level, default=1')
+            default=2,
+            help='The minimum transaction count per mixing level, default=2')
     parser.add_option(
             '--donateamount',
             type='float',
@@ -315,11 +315,11 @@ def get_tumbler_parser():
             '--timelambda',
             type='float',
             dest='timelambda',
-            default=30,
+            default=60,
             help=
             'Average the number of minutes to wait between transactions. Randomly chosen '
             ' following an exponential distribution, which describes the time between uncorrelated'
-            ' events. default=30')
+            ' events. default=60')
     parser.add_option(
             '--stage1-timelambda-increase',
             type='float',
@@ -424,7 +424,7 @@ def get_sendpayment_parser():
         type='int',
         dest='makercount',
         help='how many makers to coinjoin with, default random from 4 to 6',
-        default=random.randint(4, 6))
+        default=random.randint(8, 10))
     parser.add_option('-S',
                       '--schedule-file',
                       type='string',

scripts/joinmarket-qt.py

@@ -136,7 +136,7 @@ def getSettingsWidgets():
     sMM = ['', (2, 20),
            (0, jm_single().config.getint("GUI", "max_mix_depth") - 1),
            (0.00000001, 100.0, 8)]
-    sD = ['', '3', '0', '']
+    sD = ['', '9', '0', '']
     for x in zip(sN, sH, sT, sD, sMM):
         ql = QLabel(x[0])
         ql.setToolTip(x[1])

scripts/qtsupport.py

@@ -554,7 +554,7 @@ class SchDynamicPage1(QWizardPage):
         sMM = [(0, jm_single().config.getint("GUI", "max_mix_depth") - 1), (3, 20),
                (2, 7), (0.00000001, 100.0, 8), (2, 10), (0.000001, 0.25, 6),
                (0, 10000000)]
-        sD = ['0', '6', '4', '30.0', '4', '0.005', '10000']
+        sD = ['0', '9', '4', '60.0', '2', '0.005', '10000']
         for x in zip(sN, sH, sT, sD, sMM):
             ql = QLabel(x[0])
             ql.setToolTip(x[1])
@@ -655,7 +655,7 @@ class SchFinishPage(QWizardPage):
         sMM = [(0.0, 10.0, 2), (0.0, 10.0, 2), (2,20),
                (1, 10), (100000, 100000000), (10.0, 500.0, 2), (0, 100, 1),
                (0.0, 1.0, 3)] + [(0, 10000)]*5
-        sD = ['1.0', '1.0', '2', '1', '1000000', '20', '3', '0.25'] +\
+        sD = ['1.0', '1.0', '2', '2', '1000000', '20', '3', '0.25'] +\
                  ['55', '15', '25', '65', '40']
         for x in zip(sN, sH, sT, sD, sMM):
             ql = QLabel(x[0])