Implement reverse for the remaining operators #128
Description
As a user I want to be able to generate source changes that track through all operators (where possible).
These operators currently don't implement reverse and therefore can't generate source changes:
- mod
- bit and
- bit or
- bit xor
- shift left
- shift right
- length
- equals
- unequals
- comparison operators
- concat
Note: For some it is not possible to implement the reverse function (or only in very few edge cases).