Cardview: fix remaining known bugs and polish the UI a bit

 * abandon unresolve delegates usage, which doesn't work well with a Repeater view.
 * simplify the anchoring condition (now it simply depends on Drag.active)
 * change the ordering of cards to have all card in a group on same z value so that childAt works well
 * remove useless "temporary item resolving"
 * introduce a little animation for angle and translation
 * fix bugs where artefacts appeared in certain drag situations

Signed-off-by: Christophe Chapuis <chris.chapuis@gmail.com>