Added support for a series of capabilities, including rPI support

[Chluz]

The series of commits adds the following capabilities to netbox-agent;

• Support for rPi: leveraging /prc/cpu and additional commands instead of dmidecode which is not functions
• proper handling of bridges with parents by using brctl
• automatic setting of VRFs for IPs and interfaces, as a function of what is set in the config file
• automatic setting of primary IPs and mac: primary IPs cannot be guessed, so they are the first in the list
• assignement of DNS name from fqdn name hostname -f
• additional bugfixes

[ribetm]

Thanks a lot for this PR ! I'll try to take a look in the following days