Netwalk

- Minor fixes
- Dependency upgrades

- BREAKING CHANGE: .switch attribute renamed to .device
- Lots of stuff. Like seriously, lost track of it. My fault.

- Better device lookup, should no longer have duplicate Device objects
- Introduced callback function in Fabric.init_from_seed_device to allow external control whether to scan a discovered device or not (helps speeding up discovery by discarding those devices that are known to be inaccessible)

Juicy stuff:
- Switch is now a subclass of Device, a generic object for unmanaged devices
- Neighbors are now always defined as Interface objects when creating a device inside of a Fabric
- LLDP neighbor parsing
- Calculate an integer to sort interfaces sensibly
- Support for routed tagged interfaces ("encapsulation dot1q")
- New Extra: import stuff from Meraki dashboard to Netbox
- New Extra: run netwalk across a network importing data from Netbox

Minor stuff:
- Sessions to devices are now correctly closed
- Add attribute mgmt_address, do not connect to devices via hostname alone

- Do not delete line from unparsed_lines if no PO interface is found

- Add parsing of port channels