Taisync support

# Conflicts:
#	QGCCommon.pri

Moving Android to GStreamer 1.14.4

Off my own server during tests

Remove telemetry heartbeats

Rover isFlying check fix

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.

PARAM_VALUE parsing changes, Rover hack fix

Hack to allow Rover setup pages to work

Assume non autopilot components follow current mavlink param_value spec

CustomCommandWidget.qml:Fix URL

Fix bad cast, which truncates free storage value.