Initialization Module

[michaelbynum]

Fixes #3878

Summary/Motivation:

This PR adds a module to devel called initialization. The goal of the module is to provide methods to help initialize nonconvex nonlinear programming problems.

Changes proposed in this PR:

• Add initialization module
• Add an initialization method that uses a global optimization solver to find a feasible solution
• Add an initialization method that builds a linear programming approximation using linear least squares
• Add an initialization method that builds a piecewise linear approximation and iteratively refines it

Legal Acknowledgement

By contributing to this software project, I have read the contribution guide and agree to the following terms and conditions for my contribution:

1. I agree my contributions are submitted under the BSD license.
2. I represent I am authorized to make the contributions and grant the license. If my employer has rights to intellectual property that includes these contributions, I represent that I have received permission to make contributions and grant the required license on behalf of that employer.

[michaelbynum]

See #3878 for the changes I had to make to contrib.piecewise.

[michaelbynum]

Thanks for updating the imports, @blnicho!