Endless-sky Release v0.10.6

This is a stable release, focusing on bug fixes and other small improvements.

These changes include:

The Gatling Turret and Javelin Turret now each require one crew member.
The timer ship in "Sad Archie" has been given the "ramming" personality to improve its consistency.
Animated ship and planet sprites are now correctly rendered in the hail panel instead of not being rendered at all or being rendered at a high frame rate.
Gave the stock Dreadnought its fourth Torpedo Launcher back that it had lost in a previous release to make room for a bigger battery; it didn't need the bigger battery.