Created Matrix class

Created a Matrix class. It can multiply two matrices and has a multitude
constructors.
It can also be converted to a vec3 or vec4 if it has only one column. It
has some rudimentary dimension-checking.
This is used (mainly, so far) by the Linear SystemsSolver
Created LUDecomposer

LU Decomposer class that can also solve the system for which it
decomposes a particular matrix. Translated from Numerical Recipes for
Java.
Created LinearSystemsSolver

Created the LinearSystemsSolver. It takes a linear system as input and
solves for x using LUDecomposition. This is the class that was renamed
from "HeinSeLinearSolver" (just to clear up any confusion).
Created Vec4 class

This is very similar to the vec3 class, except that it is for 4
dimensions. So far, it doesn't have the functionality to do cross
products, but it hasn't been necessary up until now.