Remove pyof PortFeatures from `Interface`

[erickvermot]

The Switch() class is pyof dependent, which is not in agreement with the idea of having a protocol independent kytos core, nor that of working with multiple pyof versions.

The class should hold the information it is interested in its own way, and not the features instance from the features_request message itself. This would prevent napps to depend on info structure that will be no longer present in future versions (like lldp which depends on features.ports, which is no longuer present in v0x04).

[diraol]

Yes @erickvermot you are right. We really need to make the Switch class more agnostic. To do so, we need to specify some basic features that would be always present, no matter the protocol that is being used on that switch's connection. I have some ideas about it, which include some Object Oriented patterns.

But, for now, we won't be able to include this on 2017.1. So we will postpone this discussion for the next major release.

[hdiogenes]

The original issue was "fixed", but the problem moved to the Interface class.