general phase models

[OmerRonen]

We want to implement a general phase model with an additive component for each phase

[OmerRonen]

@JerryJia00 I got you started by implementing the class DynamicEstimator in the dfigs file.
You need to finish the TODOs and then test this model with our data against the dynamic FIGS, and produce the bar plots.
Feel free to reach out if you have any questions, please work on the branch https://github.com/OmerRonen/imodels/tree/6-general-phase-models

@aagarwal1996