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.
Several fixes for the cisco_topology view

- fix form's destination url
- fix position of the submit button
- Add a title
- Use dropdown menu instead of text input for switch selection
- Store nexus switch port assignments in the quantum proposal instead of using
  the node objects. This makes creating the config files much easier. And will
  also allow moving the topology editor into the quantum proposal view at some
  point