UI improvement for the banner

This commit provides a nicer banner, that can also display the
type of page that is being displayed, and that can take less space
when in landscape.
More UI fixes

This new set of UI fixes adresses post display and
comments.
Model with load previous and fixes in comments

This commit provides a system of model
that allows loading previous entries.
It also provides that feature for
comments displayed in posts.

An UI that takes care of displaying the
load is also provided.