Add trigger mechanism

[alexandertuna]

Hi @iperezx ! Here's a a draft PR of adding a trigger to main.py.

• Let me know if you have suggestions about the structure
• I'm not sure how to get the latitude and longitude of a sage node. Do you know how?
• I put almost everything into a Trigger class to avoid polluting main.py - is that okay?
• I tried to follow existing style and didn't do type hinting or docstrings - is that okay? Should I add them?
• I stared at logic a bit and I think self.farsiteParams is not necessary, but let me know if you disagree
• I haven't added binary classifier
• I haven't made a command-line arg (I guess we will want that)

Based on:

• https://github.com/iperezx/edge-plugins/blob/composableSys/plugin-smokedetect/src/main.py
• https://github.com/iperezx/edge-plugins/blob/composableSys/plugin-smokedetect/src/composableSys.py