Gurobi get_status

[maviatorTH]

Adds Gurobi status getting for all optimizer calls. Other optimizers not supported. Automatically handles status 4 by setting Params.dualReductions = 0 and re-optimizing. Feature is backwards-compatible; optimizer wrapper returns None if the get_status flag is set to default and the optimizer fails to produce an optimum or sub-optimum.

This feature improves compatibility with some polytope libraries that need to distinguish between solvable, unbounded, and infeasible cases. The only cases impacted are finished in pre-solve, and only if the get_status flag is set. Overhead should be minimal.

Small cleanups were added to affected code. Whitespace was edited to conform to more common pythonic style standards. A few documentation corrections were made as well. I will remove any style updates upon request.