Dynamical System Learning with Inputs

[EthanJamesLew]

Summary

• add a concept of optional inputs to systems, system trajectories, and estimators

• [x] Trajectories with Inputs

• [x] Estimator Bases with Inputs

• [x] System Bases with Inputs

• [x] Koopman with Inputs - [ ] SINDy with Inputs

• [x] Convenience Function with Inputs

• [x] Updated Tests

• [x] Updated Docs

[EthanJamesLew]

pySINDy is broken for me. I'm going to leave it out as the PR is so large already.