glusterd: Backport of vme table changes from master

This patch backports the following changes from the master branch

99fe09f glusterd: Moved the volume entry table to a separate file.
e306d08 glusterd: Changing the volume entry table's representation.
eac54f6 glusterd: Added option description, and validation function fields.
bcb4235 glusterd: Added validation function for performance cache max and min size.
8897d08 glusterd: Added validation function for quota-timeout.
4579609 glusterd: Added validation function for stripe-block-size.
6788bad glusterd: Fix some options in vme table
549231d glusterd: Added the validation function for subvols-per-directory
9636e63 glusterd: Added description for nfs.transport-type option in volume set help.

Change-Id: I4a64ad94f17df4b45a3a32262a83e2c35fb5f7da
BUG: 907311
Signed-off-by: Kaushal M <kaushal@redhat.com>
Reviewed-on: http://review.gluster.org/4956
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>