[Validator] Change detection of errors to not mistakenly report warnings with the string error in the message as an error. Also correctly report warnings from xcodebuild as warnings

banana-lib (libPusher) has a Ruby script which breaks `Style/WordArray`

[Validator] Error when xcodebuild fails

This bug was never shipped in a release, it only existed in master and
thus is not a change from the previous release.

This reverts commit 67514193.

Support for Frameworks / Swift

[Refactor] Rename Installer#determine_dependency_product_type to #determine_dependency_product_types

Thanks @segiddins.