Update to the QGCComboBox to use a textRole in the case where it's availble.

Some small theme colour fixes.

Updating the items to be inline with the theme.

Fix Mocklink UI

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

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

When dealing with an automatically configurable video stream, handle the video source automatically as well.