Add Cassettes (fiber/copper) device types to Netbox

[swickstrom]

Request to add cassette device types.
The user would create the cassette device type in two different racks and then specify the interconnection trace the cassette group hosts.
e.g.:
The user would create a cassette in rack101, specify the cassettes mate was in rack 102. Next they would specify the two device interfaces the cassettes host i.e.: serial.console.server.01-rack101/port.01 is connected to server.01-rack102/serial.01.
So cassette.01-rack101/port.01 would show serial.console.server.01-rack101/port.01 and cassette.02-rack102/port.01 would show server.01-rack102/serial.01.
It is most important that the cassette interfaces have no associated type; that they would be able to host whatever interface type the user specifies; this would allow representation of serial-over-RJ45 and Ethernet over RJ45 in the same interface list.

[swickstrom]

This issue could also be solved by creating a passthrough interface type.
A passthrough interface setup would look like:

Device.01|Interface.01->Cassette.01|Passthrough.01<-->Cassette.02|Passthrough.01<-Device.02|Interface.01

This means the passthrough interface type would have connections on either side to illustrate the full linkage.
It is imperative that the passthrough interface type have no required port type; allowing anything to be represented as passed through (this includes console/management/interface/PSU connections).

[jeremystretch]

It sounds like you're describing physical plant tracking, which is covered by #20