Python comparison operators: ==
Python comparison operators: !=
refactor python_comparison.py to reduce duplication
Python comparison operators: >
Python comparison operators: <

+ also some additions to the TODO list (warnings/excpetions)
Python comparison operators: >=

+ element_notequal renamed to element_not_equal
rename "lower than" to "less than"
Python comparison operators: <=
Merge branch 'feature/python_comparison_operators' into develop