Allow multiple parameter files
Imported issue: Initially reported by Alexander Kruppa in https://gforge.inria.fr/tracker/?group_id=2065&aid=16712
cadofactor.py should accept multiple parameter files on the command line, or support an include= mechanism, so that parameters can be separated into different files for input-number dependent parameters and site-dependent parameters.
See thread
http://lists.gforge.inria.fr/pipermail/cado-nfs-discuss/2013-November/000217.html
http://lists.gforge.inria.fr/pipermail/cado-nfs-discuss/2013-December/000222.html