Includes:
Command reference TOC changes
Peer command topic
Peer channel command
Addresses review comments

JIRA https://jira.hyperledger.org/browse/FAB-8179

Staged on http://fabricdocs1.readthedocs.io/en/issue-fab-8179/



Change-Id: I86bf37b1ad3239ccd2ea89c2ebf959f1b2ec4349
Signed-off-by: Anthony O'Dowd <a_o-dowd@uk.ibm.com>
Signed-off-by: David Enyeart <enyeart@us.ibm.com>