Mlsm

- Added docs
- Improved Model.execute validation
- Returns errors during `self.fcn()` in a results field `results/model/version/_error`
- Also returns errors for input field validation in the same way
- Added initial model testing framework

- To the results stored in MongoDB, add `_timestamp` and `_current` fields to allow cleanup of old results and easy querying of current results
- To the results stored in MongoDB, under `model/version`, add `_status` to indicate whether or not, at runtime, the results were `active` or `draft`
- Major: Changed input data format for `RunModels`, `RunSummaryModels`, and `RunModelsAll`:
- `data` argument of `record/records` now expects structure of `data/model.name/model.version`
- Allows for querying different data sources/logic between different models

- Add optional functionality to store only results in a MongoDB

- Initial release