Introduce wb.RepoApi which queries the repo independent from the current wiki

I've changed the wikibase api javascript to work from the client wikis as
well. At the moment they only work on the repo wiki which blocks further
development.

To achieve this I'm using CORS for requests to wikis not on the same
domain. Furthermore this fetches the edit token from the repo at it's
own, if needed (introduces wbRepoEditToken). The whole module has been
renamed to wb.repoApi to reflect this (I've replaced all usages and it
passed all Qunit tests).

On top of this this enables the Qunit tests in /lib for both clients and
repo while they used to be only run on the repo.

Change-Id: I3d256aa4dd272763e09fb9040de64ce2e8fc2b6f
Merge "Introduce wb.RepoApi which queries the repo independent from the current wiki"