Update nav protos and documentation to use millis

[Taztingo]

Summary

We are in the process of updating our navs to use millis, and we should also update the protos + cli portion to use them.

Problem Definition

This is needed for the other work we are doing on the backend for millis.

Proposal

1. Update protos
2. Update cli
3. Update documentation
4. Think about USDDenom if it should be either "usd" or "usdmilli"

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[iramiller]

Oddly enough it isn't the SI prefix milli it is the official currency denomination of mill. So in this case we would be using the term usdmill just like usdcent, etc...