CB-12050 ios: Create shared scheme for framework target, for Carthage support

[khawkins]

Platforms affected

iOS

What does this PR do?

Adds a shared build scheme for the Cordova framework target of the iOS project, which is a prerequisite for Carthage support.

What testing has been done on this change?

1. Manually ran Carthage against this change, to ensure that it was able to download and build the framework target.
2. Imported the resultant framework into a test iOS app (Objective-C), instantiated a CDVViewController instance, added the default configuration to the app (config.xml, www/index.xml), and verified that the expected view would load at app startup.

Checklist

• Reported an issue in the JIRA database
• Commit message follows the format: "CB-3232: (android) Fix bug with resolving file paths", where CB-xxxx is the JIRA ID & "android" is the platform affected.
• Added automated test coverage as appropriate for this change.

NB: There are possibly scenarios where automated testing of Carthage support could be considered, but I'm not sure what that looks like at this point.

[shazron]

Good stuff, tested it, it works as you described.
Two issues related to using module import using @import Cordova; which I will address in a separate PR though:

[shazron]

Posted #298