build system cleanups

- load(qt_module) => load(qt_build_config)
- remove:
  - CONFIG+=module (obsolete)
  - setup of PKGCONFIG* variables (automated now)
  - code relating to module version headers (automated now)
  - %mastercontent assignment (automated now)
  - pointless QPRO_PWD assignments
  - qmake -project boilerplate

Change-Id: I64ce8134c471ccf674b6815878b4090a7eb8d961
Reviewed-by: Joerg Bornemann <joerg.bornemann@nokia.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>