Working ObserverAI and watch_replay.py

[SoupCatcher]

This works for me:

python3 watch_replay.py some/replay.Sc2Replay

[codecov-commenter]

Codecov Report

Merging #138 (6e10320) into develop (a870c62) will decrease coverage by 0.90%.
The diff coverage is 0.00%.

@@             Coverage Diff             @@
##           develop     #138      +/-   ##
===========================================
- Coverage    79.75%   78.85%   -0.91%     
===========================================
  Files           93       94       +1     
  Lines        12291    12434     +143     
===========================================
+ Hits          9803     9805       +2     
- Misses        2488     2629     +141     

Impacted Files	Coverage Δ
sc2/observer_ai.py	0.00% <0.00%> (ø)
watch_replay.py	0.00% <0.00%> (ø)
sc2/bot_ai_internal.py	85.26% <0.00%> (+0.36%)	⬆️

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[BurnySc2]

I'd like to add a test that runs the watch_replay.py file in CI, so that I get notified every time I break the Observer class.

But for that I need a replay file. And that replay file might be incompatible with different python-sc2 versions, so I'd have to generate it in the CI. Additionally the replays may only be watched if the map file is available, but the docker image should have those. This is just me speaking my mind and what needs to be done before merging this PR.