Feature #2494: The scheduler looks for LIMIT_MB in DS template
Feature #2494: Change the meaning of limit_mb, add it to oned

Now limit_mb does not replace total_mb. It is the max amount of
storage that OpenNebula will use, regardless of the total disk
or the usage of the disk outside the DS dir
Feature #2494: Pretty print DS limit_mb in CLI and Sunstone, add it to sunstone DS wizard
Merge remote-tracking branch 'origin/feature-2494'