Proof-of-concept KSP-Style NavBall visualization for orientation [WIP]

[chhtz]

See screenshot for a comparison with "OrientationView"

See http://wiki.kerbalspaceprogram.com/wiki/Navball for explanation of a "NavBall".
Advantages:

• Visualizes heading and attitude within same widget.
• No singularities when pitch is near ±90°
• Also, current OrientationView has a bug that displayed pitch angle depends on window size

Texture is taken from this thread: http://forum.kerbalspaceprogram.com/index.php?/topic/63113-making-high-contrast-nav-ball/

TODO:

• Overlay (border + level indicator)
• print heading in degrees (optional)
• make texture customizable?
• make coordinate system customizable?
• show direction of movement (prograde and retrograde markers)

[saarnold]

Looks very nice 👍
Having fields underneath showing the current roll, pitch and yaw in rad and degree would be good as well.