fit values and parameters should be captured in cansas1D xml

[butler]

There was an old ticket to make the parameters from a fit available as an xml output. We currently can copy the values to clipboard in a way that pastes nicely into xml and satisfies the base requirement.

For the GUI refactor we should be more "disciplined and professional." Also we should think about the idea of wrapping information into one file given the push to provide complete provenance information into files.

A suggestion would be to have the "save as" of an entry in the data explorer save everything under that element in the tree into one xml? Of course parameters and all the fit information besides just points in the fit should be in that file (e.g M2[xxxx.dat])