Markdown Cleanup - Part 2

Now everything is in markdown...
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.
Added comments to sync.h to make it easier to understand the macros