1.6.3

App updates:

1. Toolbar customization (Google Play)

Core updates:

1. Calculate density for all bodies without geometry
2. Update number formatting
3. Localization updates (Belarusian, Simplified Chinese)

Content updates:

1. Add masses for the solar system bodies
2. Localization updates (Belarusian)

celestiamobile/Celestia@3aafa1e
celestiamobile/CelestiaLocalization@142e3c4
CelestiaProject/CelestiaContent@321e0da