Pass the user build configurations to the Pods project

This is related to #1217. If the user project has more that just the *Debug* and *Release* configurations then the  `STRIP_INSTALLED_PRODUCT = NO` setting can not be applied at the project level since only the *Debug* and *Release* configurations are created at the project level.

If the user project has an *App Store* configuration, it must be specified in the Podfile like this so that all the configurations are created at the project level:
```ruby
xcodeproj 'SampleProject', 'App Store' => :release, 'Debug' => :debug, 'Release' => :release
```