Added demo layout, sample implementation for minimal theme and sample implementation for mf54 theme. What is not so nice here is that there is no way to provide widgets to other themes, without knowing the list in advance. Gadgets are better in that respect.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@32004 20353a03-c40f-0410-a6d1-a30d3c3de9de