Added a note to the docstring of determine_day().

Added a note of a better way to determine the radio button selected by the user but due to a bug in PySide, the solution can't be implemented.
Correctly select radio button of congregation in DB.
Fixed up the docstring for the submit_edit method.
Added a note,

This method may be used by other mods in the future. Consider moving it to congregation.py
Added ability to edit day of the week radio buttons.
Removed the else clause from the determine_day method.

Removed he else clause from the determine_day method because Saturday is clicked by defult making the else: clause irrelevant.