WEB: Use descriptive support levels in compat page.

This removes the old (and confusing) percent values and replaces them with
a simple scheme of: unsupported, playable and completable.

A initial adaption of the compatibility page of the development version has
been done. This might need some reclassification! All the old compatibility
pages keep their percent values.
WEB: Change support levels to Untested/Broken/Good/Excellent.