Update Interfaces Initializer for Netbox 2.7 ...

The interface database model has changed in Netbox 2.7.
Therefore the initializer code, that was used before, broke.
As a user, you will need to update your dcim_interfaces.yml
file as follows:

- Make sure the type is a value out of the possible choices.

See the diff of this commit for further information how this is meant.

Fixing typos.

Fixed further requirements.

Fixed aesthetics.