doc: Cleanup.

Signed-off-by: John Wilkins <john.wilkins@inktank.com>
doc: Moved to separate section for parallelism.

Signed-off-by: John Wilkins <john.wilkins@inktank.com>
doc: Rewrote monitor configuration section.

Signed-off-by: John Wilkins <john.wilkins@inktank.com>
doc: Moved PG info to separate page. Moved heartbeat to mon-osd doc.

Signed-off-by: John Wilkins <john.wilkins@inktank.com>
doc: Added heartbeat configuration settings.

Signed-off-by: John Wilkins <john.wilkins@inktank.com>
doc: Added entries for Pool, PG, & CRUSH. Moved heartbeat link.

Signed-off-by: John Wilkins <john.wilkins@inktank.com>