Progress config reference for networking

This update structures and fleshes various sections of the
configuration reference for networking and misc other changes,
including:

* making a new section for RPC as related to networking
* splitting out plugin tables into a separate file
* sectionin out tables for other sections
* adding zeromq to the RPC section for compute

patchset2/3: fixes whitespace

patchset4 fixes based on review -thanks!

Change-Id: Ic2dc88118f5057c985bfe4cf5671ac9c9f8b2c6e
bp:restructure-documentation
Merge "Progress config reference for networking"