Update custom example to latest changes

Also fixed custom build

remove warning caused build failure

Modified support for multiple first run pages. Added first run for offline vehicle settings.

Rework Fly View into separate layers which can be customized at each layer.

Major update to simplify and document the custom build example

Use parsebin for automatic stream demuxing and parsing; Automatically insert rtpjitterbuffer for RTP streams to avoid video stuttering

qobject_cast is times faster then dynamic_cast for objects
that inherit QObject. also, use auto keyword to not repeat
the class name

qobject_cast is times faster then dynamic_cast for objects that
inherit QObject. Also, use auto keyword to not duplicate the
name of the Class

Fix gimbal indicator so that angle values match the markers
Select thermal mode on thermal menu selection

Custom vehicle selector now affected by theme change. Cosnistent with other actrive elements