Split the monolithic cmCPackIFWGenerator source into three parts:
cmCPackIFWGenerator, cmCPackIFWInstaller, and cmCPackIFWPackage
to isolate the implementations somewhat.
Add a COMMON option to the cpack_ifw_configure_component command to make
the data component common to its parent group.
Change the default packaging method to ONE_PACKAGE_PER_COMPONENT.
This is not incompatible because the CPack IFW generator has not
yet been in a release.