Make pod install take an optional podspec file to install the dependencies of instead of looking for ./Podfile

Add a dummy xcconfig file to the template and base the target configurations on. Also fix a few more other settings in the template. Closes #1.

Add a quick and dirty way to create a xcconfig file that the app bases its target configurations on.

Start on simple resolving. We don't try to fix conflicts yet to keep things simple, so for now that's up to the user.