Add conditional plumbing to NodeDefinition

Hello @eford1, @nicks, 

Please review the following commits I made in branch 'kyle-conditionals'.

51f3dd28c59eeb6886dacdafc87bf44a432961f7 (2013-08-09 10:29:29 -0700)
Add conditional plumbing to NodeDefinition


R=@eford1
R=@nicks