Connection type JSON struct

First run at the (cellular) connection info JSON struct based on data from: https://docs.google.com/spreadsheets/d/16csKPy0dC2Hs6OHbLdWf0qlDiiRreqPtsMEE8vebRYo/edit

* `ceiling` value is in kbps (kilobits per second). I initially used MiB/s, but there is some precision loss when I do that, and I wanted to keep it faithful to the numbers that are usually used in the standard specs. That said, when we report them in the UA, I think we should still convert these to MBps or MiB/s. 
* `type` could arguably live in a comment, but I'm erring on the side of too much information, and it might as well be structured data? It's a non-trivial exercise to map some of the different connection types across different platforms to a consistent name. 
* `latencyRange` is in ms. Once again, erring on the side of too much info. 

The reason I'm erring on the side of "too much" is because finding a good source of structured data on this stuff is really darn hard, and perhaps this could be it -- pull in this JSON and you have all you need. On that note, I'm also entertaining making ceiling an object with two values: uplink, downlink.

Am I crazy? Feel free to tell me that I am. :)