Initial Quantum Cisco Plugin Support

This commit adds initial support for Quantum Cisco Plugin. It introduces
new json setting cisco_support.
Keep the cisco related changes isolated in the quantum barclamp

The cisco_topology view now uses QuantumService.get_cisco_switch_value() to
find out the cisco port mapping for a node. This addresses:

https://github.com/crowbar/barclamp-crowbar/pull/637/files#r5445500
Fix the cisco related config templates:

nexus.ini:
- Only generate one [[switch-IP]] section per switch-ip. It was previously
generating a separate section per node.
- Add empty line to improve readability of the generated file.

plugins.ini:
- There is no cisco_nexus_inventory.NexusInventory in grizzly
Remove "cisco_support" flag and make a top level option

Handle the support of the cisco plugin as a separate option on the same level
as OVS and linux bridge.
Add UI to allow editing ssh credentials for cisco switches

The cisco plugin for quantum uses ssh to access the switches, this UI allows to
add the required information to the proposal.
Fix VLAN mode for cisco plugin

- Write ssh passwords to credentials.ini
- Fix creating of nexus.ini (switchports and driver setting)
- The cisco nexus plugin needs a tenant setting in the credentials
  (This requirement  was added to grizzly recently (2013.3 release). See:
  https://bugs.launchpad.net/neutron/+bug/1202462 )
- create the .ssh/know_hosts file for the quantum user. So that ncclient
  is able to access the switches.
Move cisco switch port assignment ui into proposal view

As the information managed in the topology view it closely tied to a single
quantum proposal it make good sense to also handle it as a part of the
proposal.
This also means that the nexus switch port assignments are now stored
in the quantum proposal instead of (ab)using the node objects for that.
This makes creating the config files much easier.
Merge pull request #111 from rhafer/pull-req-cisco-support

Initial Support for Quantum Cisco Plugin