Fixed: Saw CShell.CheckShell.138: erroring out on "Null object", added appropriate handling.
Fixed: Do not call RRDTool.UpdateRRD multiple times for devices with multiple values that have RRD enabled.
Fixed: Increase replace limit of Events.ReplaceDeviceVar from 10 to 999. Fix for issue #520.
Merge pull request #34 from danfos/minor-fixes

Minor fixes