Add get dot and dot type for dvv style causality

Conflicts:
	src/vclock.erl
Make get_entry return more information for callers

Add test for get_entry
Add valid_entry function to test if a dot is a valid format
Address review comments
Address review comments (fix docs, harden vdor validation fun)
Add a specific function for determining if a clock descends a dot
Add eqc for get_entry and descends dot
Merge pull request #463 from basho/bug/rdb/sibling-explosion

Add get dot and dot type for dvv style causality