Add a generic testcase for the cache base

Currently the cache test does cover at least the basic things like:

• Test time based caching
• Test the none-caching backend
• Check that the right css/js files are set into the additional cache data

Some additional things which would be probably nice

• Create some advanced view, with a subquery, as there has been plugin with get_results_key in the past
• Create a view which uses the node: published or admin filter, to be sure preExecute is runned on the query in get_results_key