To facilitate easier management by users and to
follow generally accepted standards, this PR moves
the following all to user home directory, subdir
.joinmarket :
joinmarket.cfg file
wallets/ directory
logs/ directory
cmtdata/ directory
commitmentlist file
User can override location with --datadir option.
An info message is added on startup showing location.
Replace links to instructions in original Wiki with updated
and corrected instructions within USAGE.md.
Add YIELDGENERATOR.md to docs/ with updated and corrected
instructions from original wiki.
Kristaps Kaupe
Adam Gibson
k3tan172
chris-belcher