Corrected reading of Matrix Market sizes and added tests

MatrixVectorReader reads an additional integer that isn't in the spec

MatrixVectorIOTest writes out the test Dense Matrix using the default printMatrixSize. However calling this without MatrixInfo causes it to assume the matrix is a sparse matrix. As a result of this, the entry count is also printed when it shouldn't.

This patch fixes these two issues and additionally provides a test for Sparse Matrices of the CompRowMatrix form