[Organizer] Fix declarative meta types registration

Explicitly register types needed for OrganizerModel;
Don't register InvalidFilter - it is for internal use only.

Change-Id: I05b754d359709f502bb8191e667835513a273d96
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Make *AbstractRequest::type() non-virtual

There is no need to protect m_type with mutex
as it only changes at construction time.

Change-Id: Id009443a6c01715a80e9cf1fbb04bc8aa18bb047
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>