Improve inter-napp dependency workflow

[ajoaoff]

Original issue opened by @diraol at kytos#141.

As I said on kytos#140:

IMHO the napp dependencies must be installed prior to the installation of the napp itself. If the installation of any dependency fails, then the process must be stopped [the best scenario would be to get the system back to the point it was before the installation was called, but lets not worry about it now].

The same goes for 'enabling' a NApp. Before enabling a NApp we need to successfully enable its requirements. Always.