some improvement for network-topology pane

[Nachi Ueno]

This bug report is a place holder for fixing some changes which I got it in the review

- display a message when there is no router, network or instance to show
- When I logged in with a regular user, clicking an external network results in an error "Unable to retrieve details for network xxxxx".
- In some case, black letters are difficult to read.
- improve layout algorithm
- improve css to change router icon
- auto update layout doesn't work

https://review.openstack.org/#/c/21916/15

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/22490

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/22490
Committed: http://github.com/openstack/horizon/commit/1cb3dc768ee45f114564cb5779c82e4cf0356f9a
Submitter: Jenkins
Branch: master

commit 1cb3dc768ee45f114564cb5779c82e4cf0356f9a
Author: Toshiyuki Hayashi <email address hidden>
Date: Wed Feb 20 14:01:52 2013 -0800

    Improve style of network topology

    fixes bug 1129190
    - display a message when there is no router, network or instance to show
    - remove link from not owned network
    - improve layout algorithm
    - improve css to change router icon
    - fix auto update layout

    Change-Id: Ibbbf55a53939ab1446f3cb36165a5cf45c27c28c