core/vm: optimisation on RETURN and updated tests

Storing tx receipts in extraDb

CLI, JSRE admin and  Solc improvements 

eth/downloader: fix test to it doesn't time out on a slow machine

eth: fix odd method names in peer set

multiple contract source for solidity compiler: returns contract array if multiple contracts. fixes #1023

Set the TEST_VM_COMPLEX env var to test complex vm tests which require a
lot of ram and quite some time.

Skipped tests due to large return value

core: block cache Has method thread safe

Allow unlocking multiple accounts

Separate accounts with spaces when using --unlock

eth: make the peer-set thread safe

JSON RPC null field updates

Nonce fix for failing transactions

Parallelise nonce checks

Add "removedb" command to Geth