Add a direct sidebar link "Manage Nodes" to allow opening nodes without administrator right

When a role is defined with role-strategy plugin only to managed the nodes and without jenkins administrator right, the user with this role have no explicit access link to the Manage Nodes Screen because he has no more access to Manage Jenkins page.

He can access by click on "Build Executor Status" link but is not a explicit link. A direct "Manage Nodes" link can be added.