Markdown Cleanup - Part 2

Now everything is in markdown...
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
Dump addresses every 15 minutes instead of 10 seconds
Merge pull request #2758 from CodeShark/CBlock-to-core

Finish moving core data structures into core.h.
Merge pull request #2771 from super3/master

Docs Markdown Cleanup - Part 2
Merge pull request #2789 from sipa/overdump

Dump addresses every 15 minutes instead of 10 seconds
main.h->core.h include dependency improvements.