[FIX] event: jump on the correct menu after installing
the event application (event kanban view).

Also added a missing description on event.type model.
[IMP] fields: split multi-purpose '_origin' into 'column' and 'inherited'

This makes it easier to determine when a field interfaces a column, and when it
implements an inherited field (with _inherits).
[IMP] fields: allow sorting on inherited field in list views