Eviscerating remnants of the old ONCvars stuff.
Wrote a tiny oneoff script that is meant to rename a column in spreadsheets.

When run as a main program, it actually does a (non-clobbering) rewrite of that column in ukvar_spread.
Wrote a straightforward test for the renamer!
Augmented the tests with more asserts (just to be paranoid).
Now everyone who loads UKvar_spread loads the right one!

With the "old_ONCvar_ID" column renamed properly.
Changed all 'output' (generated) tables to lie and say "ONCvar ID" instead of "UKvar ID".

This is a good thing, because we don't want anyone to see the "UKvar" term! says Bo