Added a target for testing Cedar-iOS.framework

Only a few lightweight specs are included for now. This could be expanded upon to run all the Cedar specs but more significant project reorganization would be required.

The copy headers phase of the Cedar-iOS target seems more reliable in Xcode 5, but this will hopefully help catch the case when that target is missing headers for other reasons.

Not sure if we are still preserving Xcode 4.6.3 compatibility, but this new target currently can't build the Cedar-iOS framework target with the 4.6.3 command line tools due to a problem with ARCHS. Maybe someone can have a look if we still want to support this.