forward with the 7.x port!

Committing in a collection of ongoing port work from #589636, so that we can stop trying to track it all in patches.

Will make merging in changes (with an outside dvcs) from the 6--1 branch easier, anyway.

First steps toward updating CTools to d7. This contains some stuff found by coder module, plus css.inc should be fully ported. No testing performed though, so theres probably bugs. Need to write some tests or something.

Allow restricting contexts via access control to allow the add content UI to remove irrelevant content.

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

- 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.