Class 2 shuttle and Delta flyer control test

Shuttle control test when automatic hovering is active. It (should) make the near-to-terrain maneuvering and landing easier.

Also analytic skylight shadow for the spacecrafts is added, adapted from Inigo Quilez (https://www.shadertoy.com/view/XdjSDy).

The HUD shows information about the spacecraft's orientation and shows the points of interest.  

At the end, Delta flyer enters the borg sphere.