Remove mdn-data dependency

[caugner]

Rari currently still depends on mdn-data, even though the same data should be included in webref.

[argl]

@caugner There are a number of spots where this is still used, the main one seems to be the cssinfo macro, also intertwingled with some l10n data from mdn-data.

Just to clarify, all this should be replaced by either webref or (in the case of l10n) by an existing mechanism in either rari or fred?