Make python plug-ins use python2 and untabify them
This MR fixes 2 things :
- On most distros,
pythonnow points on
python3. But Gimp uses
python2so this has to be enforced in shebang and in shell wrappers.
- Python does not really like space/tabs inconsistency. That's not a real problem for py2, but py3 will hard-fail on that.