Determine whether a filter should be displayed or not (based on whether any content is available for it).

Dirty code just to see how it performs with a real data. On paper, this has horrible performance, with a worst case of O(N*M*P). However, it can likely be optmized (a bit), the result is very cacheable, and I suspect that the real world performance will be much better.
ignore invalid indexes
refactored so that different cases can be handled with different functions
add support for the unlikely case where no filter is provided
removed unused variable, alpha version bump
Much slower implementation of vcontext, but it has the added benefit of actually working
bump version