Add upload and edit button to asset chooser.

The complication is that we will not know upfront the asset source that we're uploading an asset to. The possible solution would be to:

• open the "creation" dialog on top of the chooser like it used to be
• do not bind it to anything
• have a specialised save action that creates the asset on the fly and persists it

Since not all of the domains will support direct upload (probably) - we might wanna implement the availability configuration for such action.