Flight mode selector should support human-readable names

Autopilot parameter and enum requirements are often unnecessarily restrictive for end users.

While there can be benefits to being explicit about which autopilot feature(s) are active, part of the role of an interface is to provide abstractions that help users to understand available functionalities without needing to know about how they're implemented.

It would be nice to provide a mapping from known autopilot modes to human-readable names, similar to what's done in QGC. The mapping resolution process could also be used to nicely handle unknown modes (per #436).

Kurt raised this internally, in the context of the ALT_HOLD → "Depth Hold" mapping, but modes like MOTORDETECTION and POSHOLD also do not have an obvious (to a computer) mapping to a human readable term.