Add __init__ method to BaseUI for setting up pyTACS options/comm

[A-CGray]

Previously, all pyTACS classes had the same boilerplate code in their __init__ methods for setting up their MPI communicators and options dictionaries. This PR moves that code into the __init__ method of the BaseUI class which is inherited by all pyTACS classes, reducing repeated code.

[A-CGray]

Thanks for those fixes @timryanb. Out of interest, is there a specific reason you prefer calling TACSProblem.__init__ over super().__init__?

[timryanb]

Thanks for those fixes @timryanb. Out of interest, is there a specific reason you prefer calling TACSProblem.__init__ over super().__init__?

I think the first is a little more explicit than the super approach. Makes it clearer what class method is being called.

It's also consistent with other locations in the code, like here: https://github.com/smdogroup/tacs/blob/master/tacs/problems/static.py#L401