Implement polynomial simplifier with replacements

[WhiteBlackGoose]

e^x + sin(x) + 2e^x + 2sin(x) =>
a + b + 2a + 2b
=> P(a) = 3a + CONST where CONST = b + 2b = Q(b) = 3b
=> 3a + 3b
=> 3e^x + 3sin(x)

[WhiteBlackGoose]

• Entity's parent && GetMinimumSubtree using parents
• Step-by-step replacer
• Make it a little bit faster than infinity per operation