Models Moving Plan

[David Edmundson]

>
> 2 - Port _all_ code away from using ContactsModelItem

90% done.  Still one (rather tricky) usage in Contact List left, and
one usage in contact-applet.
Volunteers?

> 3 - Make GroupsModel work without ContactModelItem,
In review. See https://git.reviewboard.kde.org/r/107377/

There is a bug in this (I know because I've fixed it already). I know
of one more (I think)

> 4 - Turn ContactsModel from the tree into a list, so it's a similar
> structure to Nepomuk model.
>

This is done as a draft, awaiting a few things before I put it up for review.

Initially I will use the same roles as ContactsModel, to ease porting,
then we will come up with new roles as defined in step 6.