Document allowed address pair api

Fixes bug: 1229384

Change-Id: I8ae20374b930c74f27b487af3b493b8b7cf3d9c2
bp: pxeboot-port, provide pxboot on ports

Closes-Bug: #1226280

Change-Id: I6c3281205a80410c0d5e4215b5947bf8b4ce9ac6
author: dekehn/diane fleming
Rework directories for netconn - both are neutron

Partial_Bug: #1233748

Change-Id: I6fa1a8b194da4d90941051151a13f06786642758
author: diane fleming