Simply added copying of zValue to the deep copy functions. As tested on
OSX, this does pose any problems when duplicating an item on-page (i.e
generating a new item with a zValue equal to its original).

persistence of not required media on disk. Second step updated the cleanSource methods in classes that handle files on disk

Some warnings removed.
Fixed source url for async copyed files.

Now coping creates a full copy of already created item. Copy has it's own content (like video, audio or folder) and stores original item properties (like locked, pos, size, freezed e.t.c.).

SANKORE-774 - toolbar disabled for all items instead media and text items. It allows to calculate items bounding rect correctly.