Bootstrapping pyFAI to test without installing
start using xdg configuration ... based on the idea of FE-Picca
implementation is different.
better error message in calib if the detector is unkown

now an error message print the list of the abailables detectors.
remove ConfigParser module and useless code ?

- the ConfigParser is not used so let's remove it.
- it seems that data_files += ... was written two times.
typo, doc, error

- removed a bunch of commented code
- added some documentation
- fix some pep8 warning (mostly line too long, indent)
- i.strip -> i.strip()