Confirm child attributes are generated within configured range

[Nevakanezah]

Confirm that foals of all subtypes are spawning with attributes that fall within our expected range, as determined by the updated breeding formula.

Attributes are expected to fall within the range of:
LowestParent * skewMin% -> highestParent * skewMax%
and to be bounded within Minecraft's min and max for that stat, shown here:

Stat	Min	Max
Speed	0.1125	0.3375
Health	15	30
Jump	0.4	1.0

Llama strength is exempt here, as it's not currently modified by the plugin.
Genders like 'inbred' are also exempt, as they set specific attributes upon assignment.

[Nevakanezah]

Turns out the custom attribute formula wasn't being called because SecretHorses had supplanted it while also doing nothing. This has been fixed in the latest checkin.

While manual testing has confirmed horse attributes are thusfar landing within accepted ranges (including cases with custom skew values), I'm working on getting my automated test code running in order to verify this more thoroughly.