User session json files need a suffix convention or use `json`, and set the File Chooser dialog filter suffix appropriately.

[tparchambault]

The user session File > Save, and File > Open functionality appears to work correctly however the default suffix convention for session files has not been defined or if defined, not set in the File Chooser dialog's display filtering associated with the Open and Save functionality. The user must use the "All Files" display filter in order to locate their saved session file. Similarly the saved session file does not use a default session file suffix.