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

#607420: Visibility rules did not appear in the list when added to a pane (though they still applied).

Add a new field to allow setting a panel title from one of its panes.

Change use of "content" div to "pane-content" and "title" to "pane-title" to prevent conflicts with other things that use these fairly generic classes.

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

Fix panel page type to actually respect the contexts.

Introducing the new version of flexible which is both more powerful and comes with a javascripty visual layout designer. It is not yet flawless but it finally works well enough to commit. This commit REQUIRES the twin commit of ctools that is going in.

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.