#604976: Prevent Page Manager from throwing errors when no modules that provide variants are available.

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.

Add validation against the alias table to prevent users from creating paths that are already aliased.

Add enable/disable capability to node, user and term views. Make them disabled by default. Improve descriptions of these items.

Remove the delegator module, introduce the page manager module. Anything that previously relied on delegator module must now change its code to rely on page manager instead!