geometry.get/setPyFAI is unconsitent

[kif]

The getPyFAI method from the detector module produces the arguments to duplicate the object by calling the contructor of the detector class. This is more or less OK.

Unfortunately, this is completely unconsitent with what is done in Geometry and in derivative classes (ai, gr, ...).

[kif]

I suggest using get/set_config based on the (new) poni-file definition.