support for creating and canceling short orders
Fix asset creation and add a regression test for it.

Conflicts:
	libraries/client/client.cpp
	libraries/wallet/include/bts/wallet/wallet.hpp
	libraries/wallet/wallet.cpp
Compile fixes on windows for missing includes
Change wallet relocking code to set the relocking time relative to the local machine's current time, instead of blockchain time (which screws up automated tests that operate with the blockchain clock set far in the future or far in the past)
Improve wallet_account_balance output and remove
wallet_list_unspent_balances