Adjustments to documentation

This PR includes all adjustments to the documentation listed from

https://trello.com/c/lAGH6360/159-improve-data-model-documentation

@jh-bate @jebeck @kentquirk @nicolashery @ianjorgensen 

Please give this a once over, see if there is anything that could be explained better or just differently.  If you can think of an example that you had a question about what would happen, providing that would also be useful (I can fill in what will actually happen).
The new tooltip designs also include a display of the current I:C ratio and the current ISF from the wizard event, where available. Again, both Carelink and Insulet report these in their payload (the former is `carbRatio` and `ic_ratio_used` for Carelink and Insulet, respectively; the latter is `insulinSensitivity` and `correction_factor_used`), so I think they should also be promoted to top-level wizard attributes.