Merge pull request #81 from opennode/oms-413

Fix a subtle UserLogger bug preventing computes from changing state (OMS...
Added calling of the usage statistics update (OMS-431)
Added conversion of reported statistics from MBs to GB (OMS-418)
Updated statistic calculation to account for the VM up-state (OMS-431)
Merge pull request #82 from opennode/OMS-418

Oms 418
Added balance_limit support to billing/whmcs calls
Merge pull request #83 from opennode/oms-432

Added balance_limit support to billing/whmcs calls
Fixed a bug with incorrect return value wrapping (OMS-432)
Get HN hostname as system user even when action is performed by a restricted user (OMS-413)