Create Objects For Common Data Types

[eloiseyang]

Is your feature request related to a problem? Please describe.
Accelerator physics is centered around collections of important values, including twiss parameters, r matrices, and emittance values. One of the major design goals of LCLS-Tools is to create a common library for collecting, modeling, and computing with these values.

Describe the solution you'd like
Right now, we pass many of these values as np arrays or single values with no defined structure. It would be nice to package related values in classes with helper functions to ensure consistency across different LCLS tools.