Expand the context to allow the plumbing for replacing placeholder contexts with real contexts for preview.

More robust AJAX stuff that will eliminate some ugly errors plus prevent double clicks on ajax links.

Checkpoint checkin. Partial implementation of page task with generic subtasks, plus revamp of arguments, new access plugins (stolen from Views), updates to the wizard to make it fully compatible with the modal and some minor improvements to make it more flexible.

- a tool for AJAX, which is the next generation tool based on what Views uses.
- a tool for modals -- completely ripping the modal out of Panels.
- moving plugins for 'arguments', 'relationships' and 'contexts' into CTools.