Refactor StudentSubmission into a generic, extensible interface

[gregbell26]

I need to decide if im merging this now, or if I want to merge this once the entire project is migrated to this newer system.

The integration tests are also currently using the old deprecated system, so I'm kinda leaning to keeping this open.

[gregbell26]

Closes #20

[gregbell26]

Ok so we are working on refactoring the executors and runnables before closes this, that way we have a cleaner merge and clean out deprecated code sooner.

[codecov[bot]]

Codecov Report

Attention: 34 lines in your changes are missing coverage. Please review.

Comparison is base (540f8da) 92.02% compared to head (e8ed991) 93.13%.

Files	Patch %	Lines
...e/StudentSubmissionImpl/Python/PythonSubmission.py	92.50%	9 Missing :warning:
source/Executors/Executor.py	89.74%	4 Missing :warning:
...e/StudentSubmissionImpl/Python/PythonValidators.py	95.06%	4 Missing :warning:
source/StudentSubmission/GenericValidators.py	87.50%	3 Missing :warning:
...urce/StudentSubmission/SubmissionProcessFactory.py	86.36%	3 Missing :warning:
source/TestingFramework/Assertions.py	25.00%	3 Missing :warning:
source/Executors/Environment.py	97.43%	2 Missing :warning:
...ntSubmissionImpl/Python/PythonSubmissionProcess.py	98.34%	2 Missing :warning:
source/StudentSubmissionImpl/Python/common.py	90.47%	2 Missing :warning:
source/Executors/common.py	96.00%	1 Missing :warning:
... and 1 more

Additional details and impacted files

```diff @@ Coverage Diff @@ ## version_2_trunk #54 +/- ## =================================================== + Coverage 92.02% 93.13% +1.10% =================================================== Files 13 22 +9 Lines 890 1121 +231 =================================================== + Hits 819 1044 +225 - Misses 71 77 +6 ```

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