#841824 by levacjeep: Extend panels_edit and panels_edit_layout to allow more options with the $destination.

#844062: Turned the normal drag and drop editor into a renderer plugin, made the IPE part of it. Also some fairly serious code reorganization.

Deprecated panels_get_panels() function. This will be eventually disappear. Use panels_get_regions() instead.

Added allowed layouts to settings form for panel pages, nodes, minis.

Templatize all panel layouts; give each layout its own directory for cleanliness. Slight improvement to the API needed for the move to work.

Initial D6 work -- this includes only panels.module stuff. Right now the drag & drop display editor works, layout, layout settings and render works. Special features such as cache and styles may or may not work.