Add raw transactions RPC.

Functions added:
- listunspent
- getrawtransaction
- decoderawtransaction
- createrawtransction
- signrawtransaction
- sendrawtransaction
Fix signrawtransaction and sendrawtransaction RPC calls to support multisig redeem scripts.
Add test/documentation for 2/2 multisig address.
Add test/documentation for 2/3 multisig address.
Add support for batch JSON-RPC.
Add test/documentation for JSON-RPC (simple and batch).
Add address and account in listunspent RPC.
Add an optional parameter to the sendrawtransaction RPC indicating wether to check the transaction inputs.
Add transaction time in the getrawtransaction RPC.
RPC: gettxout

Conflicts:
	src/bitcoinrpc.cpp
added getrawmempool rpc call
Merge pull request #26 from glv2/rpc-rawtransaction

Raw transactions RPC + batch JSON-RPC