BayDAG Contribution #13: Estimation Mode Usability

[dhensle]

This PR contains a small collection of miscellaneous estimation mode usability enhancements:

• Fixes bug in stop frequency model that checks to see if the trips are in created in ActivitySim but not the survey.
• Allows the user to specify estimation data bundles that they do not want to write to disk.
• Handles empty EDBs incase a model has not choosers (can occur for really small sample sizes).
• Better error messaging and checking when loading data into larch, specifically around empty EDBs and size term selection in location choice models
• Allow comments in stop frequency spec when loading EDB into larch.

Required for SANDAG ABM3 production? -- No