Realistic Horse Genetics for 1.16.5

Version 1.16.1.1:

• Fix a crash when horseSpawnMultiplier was set to 0 and another mod added biomes of plains or savanna type with no non-horse spawns.

From version 1.16.1:

• Slight performance improvement (gene accesses are much faster now)
• Touch up war_shield.png
• Decrease default mutation chance
• Avoid crash if players summon an item meant to be unobtainable
• Champagne horses have nostrils now
• Some horses that were too dark may be less dark now