Implement horse colouration affecting attributes.

[Nevakanezah]

A prominent feature in real-world animal husbandry is the notion that specific breeds of animal can exhibit behavioural or physiological traits, and crossing these breeds can create useful hybrids.
Minecraft's horse colouration system seems an ideal vehicle to implement this kind of added complexity in a visually-accessible way.

Implement a system whereby:

• The colour & markings of naturally-spawned horses affects the max & min boundaries for each vanilla attribute. As an example:
  • Brown horses are faster but have lower health
  • Spotted horses have higher speed
  • White horses have higher health and weak jumps
• Crossbreeding results in a child whose max/min boundaries for each stat are influenced by those of its parents, similar to how attribute values are currently selected
• Possibly implement a "zero-sum" system where optimizing certain traits comes at the cost of other traits being inherently worse.
• Determine reasonable limitations for the new max/min values such that exceeding vanilla limitations is possible through optimization