Models Moving Plan

[David Edmundson]

Update:

All usages of ContactModelItem are now removed, except for one in
ktp-contact-list/contact-list-widget, to do with dragging contacts.

\o/

ContactsListModel is created and in review.

Because the name doesn't clash it should be easy to use alongside the
existing ContactsModel, and we can port all the repositories in turn,
without breaking anything. Once everything is ported, I intend to
remove it.

My AbstractGroupingModel is also in review.

I have a modified version of the contact list that uses my new model.
It is ridiculously fast compared to the old one.

I can push these as branches if people want?