Add GTPSA extension

[mattsignorelli]

Checklist

• Appropriate tests were added
• Any code changes were done in a way that does not break public API
• All documentation related to code changes were updated
• The new code follows the
  contributor guidelines, in particular the SciML Style Guide and
  COLPRAC.
• Any new documentation only uses public API

Additional context

This PR adds a DiffEqBase.value overload for the GTPSA.jl package so that GTPSA Taylor maps can be integrated.

[ChrisRackauckas]

can you add a downstream integration test that covers this? https://github.com/SciML/DiffEqBase.jl/tree/master/test/downstream

[mattsignorelli]

OK! I have added an integration test for (parametric) GTPSA maps including comparison of the Jacobian and Hessians with ForwardDiff