This does remove the feature that mining can use the internal wallet as
a source of coinbase addresses, but since Flowee doesn't actually ship a
wallet, that was just not a good reason to keep an unused class in the
libs.
Get rid of the weird boost signals setup
Move it to a new library 'interfaces' which is
for stuff that has no dependencies and can avoid
creating inter-library or cicular dependencies.
tomFlowee
TomZ