CPackIFW: Revise this generator

CPack IFW generator updates:
- Group now can have script;
- Root package (for monolithic or one package installers) can be
  configured from group.

CMake updates:
- Native installation (no Unspecified component).
Merge topic 'cpack-ifw-generator' into next

e6496b60 CPackIFW: Revise this generator