More unit tests, fix bug when running main.py

[harshil21]

Todo:

• Fix airbrakes Ctrl+C handling so I can finish writing the tests. Can be done in another PR. Currently things can silently fail in another process, which can cause memory to grow out of bounds (e.g. when packets are added to the queue and we never retrieve them) and lead to the system being completely unresponsive. Code overall needs to be more error resistant.

Bug fix:

• cyclic import when running main.py
• data processing failing because of no EstimatedDataPackets produced when first starting the script.

Other minor changes:

• better encapsulation
• make pin_factory an __init__ argument so it becomes easier to test with MockFactory in the tests later.