Minor improvements to code

[dbrakenhoff]

make Element Abstract Base Class
use builtin types to intialize arrays
use super where appropriate

[mbakker7]

Good changes.
Only remaining one I found in element.py was

def run_after_solve(self): # noqa: B027

Any reason that is not just a regular abstractmethod?

[dbrakenhoff]

Good changes. Only remaining one I found in element.py was

def run_after_solve(self): # noqa: B027

Any reason that is not just a regular abstractmethod?

Yea, this function is only implemented in some elements, the rest just uses the Element version (which does nothing). We could make it an abstractmethod but then we would have to implement it in each Base Element. Since it's only needed in special cases I figured it would be fine for new elements to be not necessarily have to implement this function.