Merge branch 'devs/cedric/evas_snapshot'

Evas snapshot feature is a new attribute for Evas_Objet_Image that allow the object to get the pixels
of the object below it in its own buffer. This can be used for two typicall use case. First is improving
accessibility by offering a magnifying glass using snapshot together with Evas_Map. Second is to make
it possible to blur the underlying content (in conjunction with filters). This should make it possible
to do some nice new theme and effect.

NOTE: As a technical note, this feature is very costly at the point. We do not support partial update
on surface and we can't know if the object below did change, so we are forced to redraw the full content
of the snapshot object for every frame. The only way to fix it is to add per surface damage detection.
I guess it is time to start rolling this in.