add tests, inc for dircache functionality

Finally have a built-in test running, currently via undocumented ctrl-shift-t
key shortcut. Initially just some very basic tests for require.js, XHR and
initial dircache support from git-html5 lib. The dircache tests will be moved
to git-html5 testsuite soon. Also update git-html5 submodule to latest bugfixes
for dircache.
impl detached head checkout for dircache tests
better err handling in tests, all tests now pass

now pointing to latest of git-html5 where all tests inc doing detached
head checkouts now pass.
renamec to Git Crx