Get rid of db dependencies on main
Moved PushGetBlocks to main.cpp to eliminate dependence of net.cpp on CBlockLocator.
Moved unrelated-to-network calls in StartNode and StopNode into init.cpp
Removed net.cpp's dependency on init.h.

Added explicit include of main.h in init.cpp, changed include of init.h to include of main.h in net.cpp.

Added function registration for net.cpp in init.cpp's network initialization.

Removed protocol.cpp's dependency on main.h.

TODO: Remove main.h include in net.cpp.
Created core.h/core.cpp, added to makefiles. Started moving core structures from main to core beginning with COutPoint.
Moved CInPoint to core. Removed GetMinFee from CTransaction and made it a regular function in main.
Removed AcceptToMemoryPool method from CTransaction. This method belongs to the mempool instance.

Removed AreInputsStandard from CTransaction, made it a regular function in main.
Moved CTransaction::GetOutputFor to CCoinsViewCache.

Moved GetLegacySigOpCount and GetP2SHSigOpCount out of CTransaction into regular functions in main.

Moved GetValueIn and HaveInputs from CTransaction into CCoinsViewCache.

Moved AllowFree, ClientCheckInputs, CheckInputs, UpdateCoins, and CheckTransaction out of CTransaction and into main.

Moved IsStandard and IsFinal out of CTransaction and put them in main as IsStandardTx and IsFinalTx. Moved GetValueOut out of CTransaction into main. Moved CTxIn, CTxOut, and CTransaction into core.

Added minimum fee parameter to CTxOut::IsDust() temporarily until CTransaction is moved to core.h so that CTxOut needn't know about CTransaction.
Moved CCoins, CTxOutCompressor, CTxInUndo, and CTxUndo to core.
Removed script.cpp's dependence on main.h
Moved UpdateTime out of CBlockHeader and moved CBlockHeader into core.
Using boost::signals2 to message main from net.cpp.
Removed the main.h include from net.cpp.
Merge pull request #2154 from CodeShark/dependencycleanup

Clean up code dependencies