Remove CodeX and CodeXTab themes

Users that were using those themes will now use the default one.

Change-Id: I20a948defaa694d181e4191911dcf7e4990aa04d
Merge commit 'refs/changes/16/1416/2' of ssh://gerrit.tuleap.net:29418/tuleap into tuleap-stable-master

* ssh://gerrit.tuleap.net:29418/tuleap:
  Remove CodeX and CodeXTab themes

Change-Id: I08dc084de65fb481adf8156d39ef4867abb49f37
Tuleap 6.6.99.30

Change-Id: I9d7372bdc3b9f55a1b7f615284cf59c773f6701d