Add error message in cmake to fail early when trying to build a scripted
python package but the option Slicer_USE_PythonQt is OFF.

```bash
CMake Error at Software/Slicer/SlicerCustomAppTemplate/build-SlicerSALT/slicersources-src/CMake/SlicerMacroBuildScriptedModule.cmake:94 (ctkMacroCompilePythonScript):
  Unknown CMake command "ctkMacroCompilePythonScript".
Call Stack (most recent call first):
  Software/Slicer/SlicerCustomAppTemplate/build-SlicerSALT/Sequences/SequenceSampleData/CMakeLists.txt:17 (slicerMacroBuildScriptedModule)
```

This is caused because the cmake macro `ctkMacroCompilePythonScript` is only included when PythonQt is on.
The macro is moved to the top folder to make it available early.

From: Pablo Hernandez-Cerdan <pablo.hernandez@kitware.com>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@27345 3bd1e089-480b-0410-8dfb-8563597acbee