Add widget parameter to disable the repeat forever button

This PR adds a widget parameter to disable the "repeat forever" option. This option corresponds to the same option in a recent update of the javascript plugin.

Furthermore in this PR some basic tests for widget rendering are added and some attribute-errors in the AT widget are fixed.

As configured in ``buildout.cfg`` the tests run with Plone 4.1 by default where the bundle attribute for the js/css registry is not yet supported. Thus this PR removes the bundle attribute. @thet i'm not sure if this is really necessary or a good idea for the current test setup.