Changeset 5960

Build first real themes.

According to our interface definition a theme now is a collection of
resources (in the hurry.resource sense, see w.s.browser.resources)
registered under a certain name and with a short description string.

For now we provide the themes already present in waeup.sirp, the red
Uli and the gray Hendrik theme. As both now consist merely of
resources, they can easily be changed. We do not have to touch any
template to switch to a different theme.

The theming module also provides utilities to find all themes defined
and registered somewhere (also in other packages).