Since the code for creating and using a macaroon service is the same for
multiple projects (pool, loop, faraday & litd), the code has been
unified in lndclient. So this commit removes the macaroon service code
and instead uses the lndclient code.
Since the default key for the macaroon db is now a shared secret with
LND, faraday requires LND's admin macaroon so that this secret can be
derived. So this commit also updates all references of LND's `readme`
macaroon to the `admin` macaroon.
This commit moves the RequiredPermissions map to its own directory so
that projects importing the permissions list dont need to import all the
dependencies of the frdrpcserver package.
To avoid the frdrpc package having dependencies to other libraries and
making using the JSON/WASM stubs hard, we extract all the business logic
and RPC server code into its own package called frdrpcserver.