Disable Wallet Mode for Litecoin

disablewallet=1 allows litecoind to operate with the BDB wallet disabled.  This is known to reduce the memory necessary to operate a relay-only node by between 40-200MB.  Pool servers and p2pool nodes can also operate with the disablewallet=1 by setting their payout address to an arbitrary address managed elsewhere.  This can enhance security of mining nodes.

This branch is nearly identical to the code shipped in OMG2 which has been operating fine for relay and p2pool nodes since September 13th with some minor changes:
* Reordered to match the commit order in Bitcoin 0.9.
* Renamed to reflect the latest commits in https://github.com/bitcoin/bitcoin/pull/2901 as of October 24th, 2013
* s/Wallet disabled.../Wallet disabled!/