VLAN reservation

[sajith]

Issue is #101.

With changes in this PR, output of TEManager.generate_connection_breakdown() will be of this shape (still a dict, but represented here as JSON), as mentioned in #101 (comment), with the slight change that interface_id has become port_id:

{
    "urn:ogf:network:sdx:topology:zaoxi.net": {
        "name": "ZAOXI_vlan_10001_10001",
        "dynamic_backup_path": true,
        "uni_a": {
            "tag": {
                "value": 10001,
                "tag_type": 1
            },
            "port_id": "urn:ogf:network:sdx:port:zaoxi:A1:2"
        },
        "uni_z": {
            "tag": {
                "value": 10001,
                "tag_type": 1
            },
            "port_id": "urn:ogf:network:sdx:port:zaoxi:B1:1"
        }
    },
    "urn:ogf:network:sdx:topology:sax.net": {
        "name": "SAX_vlan_10001_10001",
        "dynamic_backup_path": true,
        "uni_a": {
            "tag": {
                "value": 10001,
                "tag_type": 1
            },
            "port_id": "urn:ogf:network:sdx:port:sax:B3:1"
        },
        "uni_z": {
            "tag": {
                "value": 10001,
                "tag_type": 1
            },
            "port_id": "urn:ogf:network:sdx:port:sax:B1:1"
        }
    },
    "urn:ogf:network:sdx:topology:amlight.net": {
        "name": "AMLIGHT_vlan_10001_10001",
        "dynamic_backup_path": true,
        "uni_a": {
            "tag": {
                "value": 10001,
                "tag_type": 1
            },
            "port_id": "urn:sdx:port:amlight:B1:1"
        },
        "uni_z": {
            "tag": {
                "value": 10001,
                "tag_type": 1
            },
            "port_id": "urn:sdx:port:amlight.net:A1:1"
        }
    }
}

Note that VLAN assignment can't be considered "done". This is just the initial part, and I wanted to get some feedback and didn't want to get hung up on getting everything right in the first round. I am planning on following this up with some subsequent changes, described in:

• Handle VLAN updates #123
• Investigate port list inconsistency #124
• Assign existing unused VLANs when possible #126
• Free/unreserve VLANs after use #127
• More tests for VLAN assignment  #129

Also note that this does not conform to datamodel 2.0.0 spec, or rely on the changes from atlanticwave-sdx/datamodel#88. Let us get that done in another round.