doc: Rewrite the console doc
doc: Rewrite the console doc

The link between the various consoles was never well understood (by me,
at least). Clarify this by restructuring the document to highlight the
few differences between these services.

Change-Id: I08991796aaced2abc824f608108c0c786181eb65

openstack/nova,mikalstill/nova,mahak/nova,mahak/nova,rahulunair/nova,mikalstill/nova,mahak/nova,klmitch/nova,rahulunair/nova,klmitch/nova,rahulunair/nova,openstack/nova,klmitch/nova,mikalstill/nova,klmitch/nova,openstack/nova