Admin features

Added following functions to the pb.AdminNavigation

    pb.AdminNavigation.add(node)
    pb.AdminNavigation.addChild(parentId, node)

addChild can be called at any time even before the parent tree node exists, this is just in case someone will ever need to do something like this. The navigation will only be built once on startup so the overhead should be really low.

i also added an adminSample Plugin to show off the admin related features.
I'm thinking a phased approach.

Phase 1:
Each request builds out a new navigation object.  The list of children is inserted and localized after the initial navigation is built out.  This way you always have access to an instance of pb.Localization

Phase 2:
On each request the session has a property "locale" updated to reflect the current "best" locale for the user.  When "get" is called for admin navigation the first time or if a property in the session, "nav_locale", does not equal the current session's "locale" property the navigation is built out and then stored in "admin_nav".  When the session's "locale" property is set and the "nav_locale" are set and they are equivalent, then use the value in "admin_nav" as the navigation.