Matrix handler now checks in the background if the matrix is CSR.

[pelesh]

Since only CSR format is supported by the MatrixHandler methods for matrix-vector product and matrix norm, these methods will now check if the matrix is CSR and, if not, return an error. When (if) MatrixHandler supports other sparse formats, we can add switch to those methods to perform computations specific to the (supported) input matrix format.

This PR:

• Removes input argument from matvec method specifying the matrix format.
• Adds member variable with matrix format ID to matrix::Sparse class. Each derived class (Csr, Csc, etc.) sets this ID at construction. This allows matvec and matrixNorm to check matrix format "under the hood".
• Resolves MatrixHandler::matrixInfNorm should not assume that the input matrix is in the csr format #180.
• Updates examples and tests with new MatrixHandler::matvec interface.

[stonecoldhughes]

Removing the "csr" parameter is a really good improvement here. Minor comments include weighing the benefits of static assertions versus conditionals for checking ; using the "using" directive; extending a variable name to be more descriptive