LW_Matrix: Perform math operations with matrices

This class can perform math operations with matrices.

It can take the definition of a matrix as a string with the values of the elements separated by commas and the rows by semi-colons.

It can also create an identity matrix given its size.

The class can perform several types of operations with matrices like add or subtract another matrix, multiply by a scalar value or by another matrix, get the determinant, get the cofactor, transpose the matrix, adjugate and invert.