Improve Documentation around Adaptive Tracking

[freemansw1]

I'm working on some new tracking code (using lat/lon), and am working through differences between PBC tracking and lat/lon based tracking. Our documentation around adaptive search in tracking has always been somewhat vague, and even I didn't fully understand what was happening upstream. After digging into it some more, I want to make the following clear:

• adaptive_stop should be in the same units as search_range, which we don't currently do the converison for.
• adaptive_step should probably be closer to 1 for most applications than what we're doing now, as it is what search_range is multiplied by.

Suggested resolutions:

• Improve our documentation both in the API calls and with a new tracking parameter documentation page around these parameters
• Add a (or multiple) new parameters to tracking functions that allow for adaptive_stop to be either set in the same units as d_max or v_max or as a multiple thereof (I would be inclined to pick one or the other, and I would lean toward picking the multiple).