Fixes 4 actions where a whitespace was inserted in the view_mode, resulting in
an unknown view_mode (' graph') in the view_switcher.
Also updates the doc to prevent people to think they can insert whitespaces in
the view_mode definition.
Pretty much completely rewritten theme with custom HTML translator and a
few parts of the old theme extracted to their own extensions.
Banner images thought not to be that huge after all, and not worth the
hassle of them living in a different repository.
co-authored with @stefanorigano
Martin Trigaux