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

Some major restructuring, catching up to CTools. This is very much in process, there is a huge list of things that need to happen here still, but this may be checkpoint usable to the strong-stomached.

Just need to get the delete button working and then go through all the contexts, relationships and arguments to make sure their forms are working.

Initial port of panels mini; still need to work on the "context" ajax stuff and convert it to the new system, but the other stuff appears to work at least a little. Also include some fixes to layouts as "id" turns out to be illegal due to Drupal setting its own id string.

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.