[uicfg] uicfg.py moves from web/ to web/views/ (prepares #2406609)
We are about to make uicfg selectable. Registrable / selectable views
and helpers live in web/views. Hence the move.
Backward compat is put in place. However CubicWeb imports of uicfg are
updated to the new location.
Experiment with the search bar. Try queries like "card sometextualcontent" or
"card wikiid index" or "345".