Endless Sky Release v0.10.4

Space exploration, trading, and combat game.
This is a stable release, focusing on bug fixes and other small improvements.

These changes include:

Various fixes and improvements to the new Coalition campaign intros.
Outfits can now be given the "unique" attribute. The player will be warned when any such outfits are about to be lost.
All controls and settings now have tooltips.
It is now possible to recall the help messages for the currently active panel on demand.