Graph builder: Make duplicated filter detection stricter.

This let us blacklist filters more easily. It also prevents the external version of an internal filter to be added to the candidate filters list unless the internal filter is disabled.
Blacklist some filters that are known to be incompatible with DVB.

This includes the internal video decoder for now (refs #730).
Updated French translation.
Updated Polish translation.
Updated Basque translation.

Refs: #2890.