LUDOC-11 misc: update filesystem limits

LUDOC-11 misc: update filesystem limits

Move Lustre filesystem limits out of "ldiskfs formatting options"
into its own section, since it also reflects limits for ZFS targets.
This change has a large amount of indent churn, but minimal content.

Other changes include:
- ldiskfs MDT journals can be up to 4GB by default
- ldiskfs OST filesystems can be at least 256TiB in size
- correct OST inode ratio table max inode count for 256TiB size
- correct OST inode ratio table to be "under 10GiB" instead of over
- increase maximum filesystem size to be "at least 1EB" for ldikfs

Clean up formatting in this section to wrap at 80 columns.

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: Iae39e103e5b4d721ff987fb8c1d0b6294f07782d
Reviewed-on: https://review.whamcloud.com/30806
Tested-by: Jenkins
Reviewed-by: Joseph Gmitter <joseph.gmitter@intel.com>