Add MessageCollection class that handles message and unread counts and a slightly extended model for it.
Add MessageCollection class that handles message and unread counts and a
slightly extended model for it.

This also removes the ugly Collection::copy() workaround for Qt issue
102754 (QTreeView storing QModelIndices internally), so the test program
will probably crash if you have an unpatched Qt.

svn path=/trunk/KDE/kdepim/libakonadi/; revision=508404

kolab-groupware/akonadi,kolab-groupware/akonadi,kolab-groupware/akonadi,kolab-groupware/akonadi