Add complete set of Juno features in Horizon; pluggable settings, etc.

[ywang]

This feature request came from the following vsm-discuss thread:
http://vsm-discuss.33411.n7.nabble.com/VSM-horizon-framework-version-update-td128.html
Version 2.0 currently has been updated to Horizon "Juno", for features that were already in the 1.0 code base when it was on Havana, however, new post-Havana features have not been added - such as pluggable settings:
http://docs.openstack.org/developer/horizon/topics/settings.html#pluggable-settings
Pluggable settings would make extending VSM much simpler for third-parties.