Updated VP simulation to have 0.05% bad pixels and info message about simulated radiation damage

Set the number of dead pixels to 0.05% based on construction data so far (zero noise), fixed an unchecked StatusCode and tidied up comments in VPDigitCreator.

Added an info message in VPDepositCreator giving the simulated cumulative luminosity, see https://its.cern.ch/jira/browse/LHCBGAUSS-2141 for details of the plans to centralise the setting of the simulation's radiation damage effects.

Goes with references update in !321 (merged)