Interfaces list - additional columns to filter from get method

[wmclendon]

additional columns that need to be filtered out from the curated default get() method and also added to Clean function for NaN cleanup:

• is_software_switch -- True or False (NaN == False)
• used_by_aggregate_or_switch -- True or False (NaN == False)
• is_vlan -- True or False (NaN == False)
• vlan_interface -- seems to map to hardware switch name ie 'internal'? (NaN == None)
• vlan_id -- probably leave in output, but needs NaN cleanup and also stored as integers without decimal points (i.e. it stores VLAN 2000 as 2000.0 in current form)
• ipv6_addresses -- list of dictionaries with keys 'ip' and 'cidr_netmask'. convert to list of ip/netmask like done with ipv4_addresses. NaN == None

[wmclendon]

columns added to base_drop_columns:

• is_software_switch
• used_by_aggregate_or_switch
• vlan_interface

[wmclendon]

closed with #15