Poor performance of DSCompiler and rebaser initialization

[afvym]

For moderately large algebras, the initialization of the DSCompiler and of the MultivariateCompositionMapper (used by DerivativeStructure#rebase) is extremely slow.

As an example, inverting an 8th order Taylor map in 3 variables takes 25s with Hipparchus, while it is basically instantaneous with other DA implementations. In this case, most of the runtime is spent in the initialization of the MultivariateCompositionMapper. See this discussion for more details.