Don't add Frameworks to project by default

[gfontenot]

There is another issue (#141) with the #add_system_framework method not
setting the path properly, but in all actuality, we could just skip adding the
default Cocoa and Foundation frameworks to new projects by default. We're
already turning Modules on by default, so these imports are superfluous
(especially since they don't actually work).

[fabiopelosin]

Modules are not guaranteed to be turned on (there were some issue with Xcode 5 and I have't yet investigated with Xcode 5.1) so the references are still needed.

[fabiopelosin]

I'm closing this ticket in favour of fixing the paths of the frameworks in #141. As explained they still serve a purpose and I think that we should keep them for the time being.

[fabiopelosin]

@gfontenot: Please feel free to continue the discussion if you disagree or have strong arguments for looking for a different solution.

[gfontenot]

I don't have super strong arguments one way or another here. I stopped adding UIKit and CoreGraphics explicitly in liftoff (mainly because it bothered me that the paths were wrong), and I haven't noticed any issues so far. I'll keep an eye on it. But if the paths are fixed, most people probably won't care (or notice) one way or the other.

[fabiopelosin]

This is a grey are of Xcode... the linker flags are needed and are resolved to the correct location at build time. The file references appear to be there just to make the headers accessible (This is why I never removed them from CocoaPods... some users were asking for them). Unfortunately there is a source tree which resolves to the SDK but it doesn't work properly and Xcode doesn't uses it (likely because it ca change just by changing target and file references are not expected to change on that event).