Linking to a Windows shared library (.dll) requires only its import
library (.lib). This teaches CMake to recognize SHARED IMPORTED library
targets that set only IMPORTED_IMPLIB and not IMPORTED_LOCATION.
- Imported bundles have the MACOSX_BUNDLE property set
- Added cmTarget::IsAppBundleOnApple method to simplify checks
- Document BUNDLE keyword in INSTALL command
- Updated IMPORTED_LOCATION property documentation for bundles
- Updated ExportImport test to test bundles