Gaia Sky

This is a bug-fix release. The procedural galaxy is drawn at the right size and position, the background grid annotations are back, and a camera teleport when focusing large objects is fixed.

• Procedural galaxy volumes are drawn at the correct size and position (they were 5% too large and off-centre). Volumes generated with an older particles-to-volume.py must be regenerated.
• Volume labels are no longer 10 times too large.
• The latitude/longitude annotations of the equatorial, ecliptic and galactic grids are visible again.
• Fixed-function GL state no longer leaks between render groups, and render-group teardown no longer skips state restoration on failure.
• Focusing an object that opts out of camera collision (e.g. the Milky Way) no longer teleports the camera out of it.
• Focus resolution no longer jumps to the first particle of a set when a name is not in its index.
• The galaxy volume is 1.37 times larger, giving a 17 kpc gas disk with the Sun at 0.47 of it, and dust scattering is enabled.