added a configuration file and library

[waridh]

#44 #61

Included

• A Python helper library that takes the path to the config file, and the subsystem of interest, and returns a dictionary with the settings needed. For now, the only field is the port.
• A configuration file of the .ini format. Chosen for ease of modification.
• A definitions.py that contains immutable shared values. Most notable is a dynamic absolute path of the project root (It will be the correct location on any machine thanks to pathlib.Path).
• Simple Pytest tests for this helper library.
• Basic documentation on how to use the microlibrary, and write new pytest tests.

[dheadrick1618]

Great work! This is a good starting point for us moving forward with testing the sim subsystems.

System tests however will be tricky with the OBC FSW interacting with the simulated subsystems.