Fix gimbal indicator display

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

Std ComboBox

Custom Example: Minor fixes for custom build controls

Joystick button state

Custom Example: Fix gimbal state getting out of the limits. Fix palette button not working if not in thermal mode. Increase zoom buttons

Custom flight modes

Stable merge

Custom fixes

Fix AirMap

Custom theme - Multi vehicle and Camera Shutter fixes

Fix Mocklink UI

Smaller border and some more distance between the circles

* Move the Multi-vehicle UI next, not under, the indicators
* Remove the icon

Custom Gimbal Control

Improve CentOS instructions

Camera mission commands

There are no editable parameters and without this, you are presented with a raw list of all 7 parameters to edit.

PR Custom example theme

Added Light theme

This is a small experiment into creating a custom theme for QGC.