Move coins.cpp and keystore.cpp to libbitcoin_common
Move coins.cpp and keystore.cpp to libbitcoin_common

Prepare for introduction of `bitcoin-tx` tool.

syscoin/syscoin,domob1812/crowncoin,Infernoman/crowncoin,Infernoman/crowncoin,Crowndev/crowncoin,Crowndev/crowncoin,Infernoman/crowncoin,syscoin/syscoin,Crowndev/crowncoin,domob1812/crowncoin,Crowndev/crowncoin,domob1812/crowncoin,Crowndev/crowncoin,syscoin/syscoin,syscoin/syscoin,Infernoman/crowncoin,domob1812/crowncoin,syscoin/syscoin,Crowndev/crowncoin,domob1812/crowncoin,syscoin/syscoin,domob1812/crowncoin,Infernoman/crowncoin,Infernoman/crowncoin,syscoin/syscoin,syscoin/syscoin