Fix bug in initialization routines to return solve with bounded nlp

[stephenscini]

Fixes # .

Fixes issue in initialization routines where the model is run through nlp solver before bounds are removed.

Summary/Motivation:

Currently: Original variables are bounded in methods and then there is cleanup but the initial point from lp, pwl, and global approximations is not verified to work with nlp_solver

Changes proposed in this PR:

• After each method "Finally: _cleanup()", run the original model again through the nlp solver and return that result.
• Additional warning added for using the global solver without specifying a time limit.

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[stephenscini]

@michaelbynum Please review when available.

[michaelbynum]

This is almost perfect. One comment below. Also, the code for the final nlp solve is almost identical in all three methods. Could you move this to a helper function?

[stephenscini]

@michaelbynum Addressed comments. Please take another look when available. Thanks!

[michaelbynum]

Thanks!