Interface to GiNaC for Simplification

[michaelbynum]

Summary/Motivation:

This PR provides an interface to GiNaC for expression simplification (although sympy can be used as well).

In [1]: import pyomo.environ as pe

In [2]: from pyomo.core.expr import differentiate

In [3]: from pyomo.contrib.simplification import Simplifier

In [4]: from pyomo.contrib.fbbt.fbbt import compute_bounds_on_expr

In [5]: m = pe.ConcreteModel()
   ...: m.x = pe.Var(bounds=(0, None))
   ...: e = m.x * pe.log(m.x)

In [6]: der1 = differentiate(e, m.x, mode=differentiate.Modes.reverse_symbolic)
   ...: der2 = differentiate(der1, m.x, mode=differentiate.Modes.reverse_symbolic)

In [7]: simp = Simplifier()

In [8]: der2_simp = simp.simplify(der2)

In [9]: print(der2)
1/x - x/x**2 + 1/x

In [10]: print(der2_simp)
x**-1.0

In [11]: compute_bounds_on_expr(der2_simp)
Out[11]: (0.0, None)

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[michaelbynum]

Thanks for all the help on this one, @jsiirola.

[jsiirola]

This is good to go!

[michaelbynum]

@dallan-keylogic, I believe we did fix the mutable parameter issue as part of the PR (with the sympy interface).