doc: Changed usage to "bucket-name". Description was okay.

fixes: #4102

Signed-off-by: John Wilkins <john.wilkins@inktank.com>
doc: Added a scenario to PG troubleshooting.

Signed-off-by: John Wilkins <john.wilkins@inktank.com>
doc: Aesthetic improvements. Removed unnecessary graphic and overrode margin for h3 tag.

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