Overhaul first l3keys test file

There is still more to do here: some tests need to be reintroduced into new
files. There is also one test to add once a bug in l3keys is fixed.


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@4534 de43f980-851b-0410-b2f7-c40aca1f87e0