factorize even better the different "skins"

[allan-simon]

On tatowiki we've started to do that for the "master" (so it should be backported here), but we're missing a way to factorize single view (i.e we need to find a way to say that we got a default view but that inherit from the skin's master while still being able to "overide" it by a custom view, without needing to recompile code)