Huge commit, not fully functional but compile succeeds.
More misc fixes.
Remove connection list from Block.
More stuff. CreateSingleStoneBlock now works.
AddStoneToBlock() now works with new group stuff.
Remove 'm_block' from Group.
Make SemiTable::m_entries an array (instead of an SgArrayList).
Add a couple misc asserts.
Prelimenary support for block merges.