Allow YG settings to be saved to joinmarket.cfg.
Before this commit, yield generator settings were
set inside the python script, which is not good.
After this commit, the order of precedence for the
settings for a yield generator is:
* Command line arguments, or
* Settings in [YIELDGENERATOR] in joinmarket.cfg, or
* default config settings in jmclient.configure.py
* yg scripts set reloffer/absoffer only:
Prior to this commit, the yield generator user
level scripts required the user to specify offer
types depending on the wallet, but only 'rel/abs'
distinction is user choice; the other element
(native segwit, p2sh or p2pkh) must be defined
by the wallet, so we now call `wallet.get_txtype()`
to translate from reloffer/absoffer to sw0.. etc.
* Taker chooses nversion, nlocktime per wallet type:
Takers who are still using p2sh-p2wpkh wallets will
not want to flag their transactions with different
tx metadata than previous versions that are still
running, so we check the `get_txtype()` output to
decide which nVersion and nLockTime to use.
Also, the SNICKER locktime is reverted to zero as
according to draft spec.
* change offer type in test_coinjoin
* update docs for bech32 wallets
This refactors YieldGeneratorBasic a bit. In particular, we move things
that custom algorithms will most likely want to change to separate
functions. That way, it is easy to define the behaviour of inputs
and outputs for the join without the need to duplicate the other, more
general logic of create_my_orders and oid_to_order.
Previous to this commit, the jmbitcoin package was accessed via
a file in jmclient `btc.py` which was originally added as an
interface to allow the client to use a non-jmbitcoin package to
provide the implementation; while this idea is useful, the way
it was implemented was not, moreover it is not currently used
and contained duplicated code that was unmanaged. Also, the
original usage of this was only by the electrum plugin, which
has currently been abandoned. This simplifies the code and
avoids spurious error messages. Note that most of the changes
are a result of pulling the logging function directly from the
jmbase package instead of indirectly via this interface (which
was unnecessary and not connected with jmbitcoin).
