Delete closure/closure-library directory to make way for updated version.
Squashed 'closure/closure-library/' content from commit 6fb5ead

git-subtree-dir: closure/closure-library
git-subtree-split: 6fb5ead969d283c0e70e04d0e32262c9fec3910c
Merge commit '0a141a72c68852ee8da346f68fac134395c2852a' as 'closure/closure-library'
Update ManifestTest to reflect changes in updated Closure Library.
Replace uses of hg in shell scripts with git.