BasicModel not setting NOT NULL on add or change

I added code for this in two sections (six places altogether) in the FannieDevelop branch.
line 793, 812, 852, 916, 944, 973
I've tested the code, but not this version of the whole program, at my site.

My attempt, modeled on 'increment' handling,  to code detection of the need to set or un-set NOT NULL that seems to be needed about line 836 was not successful.