Break panels_node_content into a module + a .inc file to more clearly represent how content types can work in a module. Also fix several notices by providing defaults for the form.

Add a new directive to content types to allow fetching information about a single subtype (i.e, view, block) rather than all at once.

View panes display plugin. Note that this checkin may break a bunch of content types because I added $subtype to some content type declarations and need to go through all the content types and update the render and title functions.

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.