Haizea

Fixed bug where VM RRs in a cancelled lease were not being properly finalized (they were not being removed from the slot table, which caused trouble).

Also, Haizea was not sending shutdown commands to OpenNebula after a cancelled lease.

Fixed: Estimating suspend/resume times with global filesystem still used old method to access requested memory

Fixed: Haizea would crash when fetching nodes for which OpenNebula had not yet collected monitoring information. This fix also has the pleasant side effect of allowing Haizea to detect new hosts added in OpenNebula without having to restart Haizea.

Switched to a saner implementation for Singleton classes. Required multiple changes all around (which had the indirect side effect of making constructors less dependent on the get_config() function)

Miscellaneous pylint-induced code cleanup.

Fixed whitespace that, while ok to Python, made epydoc barf.

Minor fixes for issues detected when running unit tests after last commits. Also removed several print statements that shouldn't be there.

Modified the accounting code so information is gathered using "probes" instead of inserting hardcoded statements throughout the Haizea code. Now, collecting additional information involves writing a pluggable probe, instructing the accounting module when the probe must be run (currently this can be at every timestep, when a lease is requested, or when a lease is done). Thus, gathering additional information doesn't require modifying the core Haizea code....

- Data persistence is implemented. It still needs some work (and has to be made configurable so it can be switched off during simulations), but it's working.
- Started to clean up the accounting code so it will collect data using "probes" instead of hard-coded statements.

Updated copyright notices.