Constraints not checked when using PGMXReader

[Miguel Ángel Artaso Landa]

When a network is loaded through the PGMXReader as it is done in the ExampleAPI project, it is not tested that the network complies with the constraints. Maybe it could be checked in order to ensure that the network fulfills all the constraints according to the networks of its type.

[Francisco Javier Díez]

It would make the parser much slower.