qobject_cast is times faster dynamic_cast for objects that
inherit QObject. also, use auto keyword to not duplicate
class names.

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

Handle crash on first time switch from disable to enabled
Handle video settings restore after disabling Taisync

Remove telemetry heartbeats

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.