Extract support project for shared code (method redirection)

[joemasilotti]

I noticed that there was shared code in the three core projects, UIKit, Foundation, and CoreLocation, all dealing with method redirection (swizzling). This PR extracts the functionality to PCKMethodRedirector in a new top-level project, Support. The three core projects then depend on this new project for their method swizzling.

The extractions required quite a bit of changes to the existing dependency management.

1. The three projects reference the new headers via a User Search Paths pointing to the Support/Core directory.
2. UIKit and CoreLocation link to the Support/Core library or framework (iOS vs. OS X).
3. FoundationCore and FoundationSpecHelper both need the functionality so depend on the Support project. Both of these are tested via the same target which requires the testing target to depend on both. This leads to duplicate symbols when creating the static library. To fix this FoundationSpecHelper now depends on FoundationCore which in turn depends on SupportCore. Note that this does not apply for Frameworks (on OS X) as these are smart enough to figure out PCKMethodRedirector.o is the same and not link it in twice.
4. All of the new logic is duplicated in the podspec to support sub-dependencies to the Support/Core project.

@idoru and I kicked off the initial extraction and I took it from there. Let's think of this PR as the beginning of a discussion as I am sure this will require some more work to be done before emerging.

It's also over 2000 changes in .xcodeproj files which, as we all know, are no fun to read :-)

[akitchen]

Thanks for taking this on. Yes, there are a lot of changes in the project config for this!

I think it would be good for us to cut a version with the rest of the recent changes before merging this one.