extend run script phase to generate a proper framework-like package in Products dir (similar to Parse.framework etc)

So, first off, I think it is nice to have a BoxSDK.framework bundle encapsulating all headers, resources, and binary. It makes it easy and clean.

On the other hand, I have found that your current way of "simulating" a bundle will only effectively work when Xcode is configured to use a common directory for derived data -- otherwise even your sample app (https://github.com/box/box-ios-sdk-sample-app) will not compile out of the box.

The change consists only in modifying the script which is run at the end of the build to package the framework.

I hope you find this useful.

Best,
Sergio