Xcode 6 Support

Changes include: #262, #258, #257 and others. This changes how tests are run under test bundles - they run under XCTest/SenTest instead of hijacking on `+load` by generating dynamic test case subclasses with test methods for each example.

Not verified on Xcode 6.1 beta on Yosemite.

Fixes the Project templates to work on Xcode 6 (and still behave correctly on Xcode 5).

Some fixup and wip commits should probably be rebased and squashed before this is merged.