doc: Update the list of fields for the pool set command.
doc: Update the list of fields for the pool set command.

This list was lacking a few fields: crash_replay_interval, pg_num,
pgp_num and crush_ruleset. Include these fields and add add short
descriptions.

Signed-Off-By: Andre Noll <4aaaf3c285f100eb4c3bf3318694b035bcec79c5@systemlinux.org>

ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph