Separate/Link compute config sections

To avoid double maintenance during the documentation restructure
effort, and to further facilitate content sharing, this patch
separates some sections of the compute configuration chapter
into separate files.

Separates vnc into 'using' and 'configuring'.

Add some status notes.

Change-Id: Ia8d1b1a30b63107922939147988ae48bdc71eaa4
bp:restructure-documentation
bp:design-content-sharing
Merge "Separate/Link compute config sections"