dnd-frame-behavior -- Change the behavior of DND frames (and resources)

[deyan]

Implement the resources and frames in the following way:

• Templates dragged to a non-selected element of the page should create a new instance (and the highlight should be green)
• Resources dragged to a non-selected element of the page should create a new frame with the resource (and the highlight should be green)
• Resources and templates dragged over a selected frame should act like now (apply template, change background or resource)
• Dragged image over the border of page should put the image as a background