ARMORY-150 - Review and correct new armoryd code

Implemented most of the requests and recommendations from the arrmoryd
code review. Among other things:

-Wallet unlocks now have a default timeout.
-Wallets may be relocked before the relock is supposed to occur.
-armoryd has proper support for the --datadir command line argument.
-Some code that caused a wallet rescan has been commented out for now.
-A README file for armoryd has been added.
-getlistunspent() has been expanded to support multiple addresses.
-getarmorydinfo() has been expanded.
-Some logic was cleaned up.