feature #1678: add monitor_ds.sh
Feature #1678: DS inserts clone & ln target attributes into each disk
(cherry picked from commit 4487c7cc62ecc14d1f6853858e17e52b6e21541c)
Feature #1678: Method to calculate VM storage usage in scheduler
Feature #1678: Filters VMs that do not fit in the image DS
Feature #1678: Make all disk related variables long long
Feature #1678: Host monitorization copies DS info to each system DS. Assumes all DS are shared.
Feature #1678: CLI does not hide system DS capacity