First commit towards name coin support - first adding merged mining!

Split Block into BlockHeader and Block : public BlockHeader.

Added AuxPow from the name coin github - enabling merged mined blocks

Added NAMECOIN script OPs

Everything still runs smoothly under bitcoin
Forgot to add the AuxPow.h file...
Further additions towards name coin support - still missing is:
* storing of merge mined headers
* verification of OP_NAME_* scripts
* testing

BUG: Litecoin has disabled version locking, causing libcoin to hang at block 419448 which had the majority quorum! - FIXED