refactor vocabularies tests
refactor vocabularies tests
follow style guide
refactor control panel tests
add option in configlet to select tiles available for cover layout creation (closes #191)
an upgrade step is provided to update the registry with the new record, but it's not working yet
see: http://stackoverflow.com/questions/16268938/how-to-add-a-plone-registry-record-programatically
fix upgrade step by including the declaration of the new field in a registry.xml file