Add support for graceful version deprecation

[nbrooke]

Right now released versions only have the concept of force updating or not. The "latestTestVersion" path gives you some more gentle upgrading, but is very simple and intended primarily for test builds.

Ideally we would want a way to more gracefully deprecate old version, for example, including a date where a deprecation is going to take place, warning periodically up to that date, and then turning off on that date.