Make MDArray aware of MDMatrix instances

[rbotafogo]

When an MDMatrix is instanciated, an MDArray sibling is also instanciated. An instance of MDMatrix can be constructed as: matrix = MDMatrix.double([5, 5]. If we do array = matrix.mdarray, then array is the sibling of matrix and both matrix and array point to the same backing store. if we do an structural change in matrix, for instance, transpose a column, then the same function is done to the array. However, if we do a strucutral change in the array, then the matrix will no be aware of the change.