Corfunc perspective save extension (.cor) conflicts

[krzywon]

The corfunc perspective application save states use the file extension .cor. NCNR USANS data also uses this same extension for its XML data.

Errors thrown when trying to load HF48a_cor.COR:

The following errors occured whilst loading HF48a_cor.COR:
 Data Loader cannot load: C:\Users\jkrzywon\Downloads\HF48a_cor.COR
 Please try to open that file from "open project"or "open analysis" menu.

The corfunc perspective has not seen a SasView release as of yet, but .cor files have been available for quite some time. I suggest changing the corfunc extension to something else (like .cfn).

[smk78]

I'm content with the change of save state extension from .COR to .CFN.

[krzywon]

In ae9b8bf0596d163a9011e6b945a6fb09f4b36456/sasview:

The corfunc perspective now saves and loads in files with the extension .crf instead of .cor. Fixes #832