Initial code for tracking market depth prior

Requires at least 1% of the shares to be on each side of the market
before automatic trading will execute for a given pair.
only allow long positions to be matched by miner
Merge pull request #59 from clar/master

further fix for issue #57: implement fc::from_variant
Merge pull request #60 from clar/master

fix issue #56: Wallet Loading Errors cause wallet to be reset
Numerous bug fixes.
May updates, adding utility to get bts balance