Normally the system will prompt the user to allow Imager access
to removable volumes.
Open preferences and ask user to allow Imager manually in a
corner case in which this does not occur.
The default Info.plist template provided by CMake doesn't have this key, and
CMake only has minimal support for settingstypically found in this file.
In order to specify NSPrincipalClass, we need to provide the whole Info.plist instead.
Info.plist is also specified as a dependancy to the application so that it will
appear in the project explorer, and changes to this file will trigger a rebuild.
