Subnet Editing (tagging)

[allmightyspiff]

Add new command slcli subnet edit

Should allow users to tag subnets ( with the newly added https://sldn.softlayer.com/reference/services/SoftLayer_Network_Subnet/setTags/ )
Should allow users to set subnet notes

[allmightyspiff]

slcli subnet detail should print out any tags a subnet has, along with its note.