Add "source" variable to CANDO compounds mapping

[zfalls]

This will be an additional variable that will be present in the mapping file and will be processed on init. Each compound will have an associated source (public db, design protocol, etc.) from which it was extracted.

• [ ] Add "source" column to compound mapping file
• [ ] Add new variable to Compound class that will be populated by "source" during CANDO init
• [ ] Optional: Output "source" in canpredict and other functions

[ManiBio]

I am trying to install this package via conda. I am getting error and unable to install the cando package. Error: "Collecting package metadata (current_repodata.json): doneSolving environment: failed with initial frozen solve. Retrying with flexible solve.Solving environment: failed with repodata from current_repodata.json, will retry with next repodata source. Collecting package metadata (repodata.json): done Solving environment: failed with initial frozen solve. Retrying with flexible solve."