Apply count compounding mastery boosts to a starting mastery level, each
step drawing its increment from the calcMasteryBoost table evaluated
at the running value.
Parameters
startML: number
The mastery level to begin from.
count: number
How many boosts to apply; ≤ 0 returns startML unchanged.
Apply
countcompounding mastery boosts to a starting mastery level, each step drawing its increment from the calcMasteryBoost table evaluated at the running value.