Add AKA to modules

[tischi]

there are currently modules about “median filter” and “morphological filters” and we feel it could be equally logical to instead have modules called “rank filters” and “rank filter sequences” that could cover the same material.

We could make it a habit to somewhere in the module have a sections where different names for the same thing could be explained. Not sure where it would be best?

ping @manerotoni @tibuch

[tibuch]

I think it would make sense to put this at the top. In case the reader knows the concept already under a different name, it would be clear immediately.