Revert "Revert "Move cross domain xhr view out of jsbox app's view definition and into the base views (using /cross-domain-xhr/ instead of /apps/jsbox/cross-domain-xhr/, which doesn't work)""

This reverts commit 58618b41fcf212f21ab41f44a2e2663e14c484ef.
Add jquery.cookie vendor lib
Add the csrf token in the ajax call instead of making the cross domain xhr proxy view csrf exempt (that was a bad idea, sorry :/)