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
Several fixes for the cisco_topology view

- fix form's destination url
- fix position of the submit button
- Add a title
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.
Use dropdown menu instead of text input for switch selection
Only show the Cisco topology editor if there Cisco support is enabled in 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 )
Don't try to process the nexus switch config in gre mode

For the gre mode (fake driver) no switches need to be defined