Revisions: Add a test case which checks the _edit_last postmeta value after a revision restore 

Also validates some of the things to be fixed for the off-by-one issues with authorship.
See: #20982, #16215
Props adamsilverstein for the original patch.


git-svn-id: https://unit-tests.svn.wordpress.org/trunk@1210 4a5a2adb-35eb-4268-9a1b-fe04a4134342