Moved CBlock::WriteToDisk out of CBlock to inline function WriteBlockToDisk in main.h
Moved WriteBlockToDisk implementation from main.h to main.cpp
Moved CBlock::ReadFromDisk out of CBlock to functions ReadBlockFromDisk in main.h
Moved ReadBlockFromDisk implementation to main.cpp
Pulled DisconnectBlock out of CBlock.
Pulled ConnectBlock out of CBlock.
Pulled AddToBlockIndex out of CBlock.
Pulled CheckBlock out of CBlock.
Pulled AcceptBlock out of CBlock.
Moved CBlock from main.h to core.h
Merge pull request #2758 from CodeShark/CBlock-to-core

Finish moving core data structures into core.h.