Fixed InvertBasicExpressionVisitor bugs with subtractions and divisions

Minus expressions and divisions were both computed the wrong way around,
i.e. a-b as b-a and a/b as b/a.

Consolidated duplicate InvertBasicExpressionVisitor code into single
base class.

Also noticed that the basicexpression parser doesn't parse e.g. `a*5/4`
but parses `a*5 / 4` just fine. Didn't dive into these parser problems
for now. Hopefully we can retire this code entirely at some point in
favor of SCL expressions.

gitlab #505

Change-Id: I74eaeae1dbec080a10ffc43c0c321705c0b0ea86