if unclean shutdown occurred, checking if last indexed doc (that is not deleted) etag is greater or equal to index stats etag
storing highest etag in index and validating against it during power failure
cleanup
Merge branch '2.5' of https://github.com/ayende/ravendb into power-failure

Conflicts:
	Raven.Database/Indexing/Index.cs
Merge pull request #1072 from ppekrol/power-failure

Power failure