Initial stab at network controller

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
first shot at skeleton of simplebridge; will merge @lk4d4's code later

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
Merge pull request #104 from erikh/extensions

Extensions