Feat(plugins): adding ability to use plugins

[link108]

This PR enables orca to use plugins. See https://docs.google.com/document/d/1KFDCIIC_abJMVczmcTqeb3XenNibFet5acN4bq9KD3k/edit?usp=sharing

[spinnakerbot]

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[robzienert]

Neat!