Summary:
Previously, it was forbidden to have two rule sets with overlapping columns,
since that could introduce an dependency on order of evaluation without
the user having a way to control that order. This diff permits such rule sets
if the are compatible in a very simple way -- all allows or all denies.
Anything more complicated (even if actually order independent) remains forbidden.
Test Plan: added tests
Reviewers: dsagal
Reviewed By: dsagal
Differential Revision: https://phab.getgrist.com/D2745