This allows parameterizing templates. Also change
placeholder syntax to `${placeholderName}` also for
existing placeholders `$target_name`and `$platform`
and generate warnings when using the old placeholder
syntax.
This allows users to set the defaultConfigurationName project wide. This
setting corresponds to the drop down in the project settings that says
"Use CONFIG for command line builds". This affects which configuration
Xcode looks in for some settings, even if you pass `-configuration FOO`.
Tom Quist
Yonas Kolb
Brentley Jones
Keith Smiley