Remove telemetry heartbeats

Move cache location methods so they are available in all builds

Add missing header

Add --clear-cache option

Fix Rover check for isFlying

Add support for Linux and experimenting with settings (there are "set" but no "get" options for them though)

On desktop (Ethernet connection), the ground unit pushes UDP directly, which makes the use of an actual "Link" not possible. Instead, I've moved all of Taisync support to a "manager" owned by QGCToolbox.
Added a Taisync settings with some basics already wired and running.

Hack to allow Rover setup pages to work

Assume non autopilot components follow current mavlink param_value spec

Fix cases of _logVehiclePrefix usage with missing componentId

Add support for Orbit flight mode

Show Orbit center from telemetry