PERF: Testing intermediate changes for using Eigen

This patch demonstrates that both Eigen and the DoLittle LU solutions
produce very similar results, thus the next set of patches will replace
more of the vnl code with Eigen code.
PERF: Avoid unnecessary matrix copies by using const references.
PERF: Move initialization of diagonal to class

The diagonal matrix could be initialized 1 time and used
many times by moving initializing it in the constructor.

Also converted from struct to class and add Eigen memory
alignment.
ENH: Use Better tolerance for different slightly differnt results

Allow for upto a 10th of a point difference.
PERF: Moving variables for better locality and less copying.
ENH: Updated baseline for making tests pass.