Major update to simplify and document the custom build example

Support for reusable InstrumentValueArea control

Refactor instrument value controls

New value editing dialogs

Icon support for values display

New grid based values page editor support

Support for built-in preset delete prevention

Expose API to prevent QGC from saving the application window size and position on close (or restoring it on open).

Move analyze page list model to the core plugin.

Move PreflightCheckList to custom builds only. The model, which used to be implemented within BuiltinPreFlightCheckModel is now within the control itself. It is up to the implementer to define a proper model.

Pay attention to the current camera auto stream capabilities directly rather than just camera changes.

Restore QGC to its normal UI layout (buttons on toolbar)

Get rid of QGCView, QGCViewPanel and FactPanel. All messages and dialogs are now handled in the root window.

Support custom build override of available complex items

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.

Allow custom builds to turn off firmware version check

Q_ENUMS is deprecated and should not be usued.
Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

Custom build override for stable version check no longer needed