Clean up use of (broken) jshashes; use built-in 'crypto' package instead.

jshashes is completely broken at the moment (see
https://github.com/h2non/jsHashes/issues/6 ).  Using crypto makes a few
more tests pass (and a few more fail) due to the totally broken
caching (all cache keys identical) in mediawiki.TokenTransformManager.js.

Change-Id: I593dfe031d43b47f42807cdd27bb74dd6dc22b17