Change default damage and white flash

Change both the damage flash and white out values to return 0 by
default.  This prevents a damage flash or white out from displaying for
GameBase derived classes that don't override these methods.  From
https://github.com/GarageGames/Torque3D/issues/395
Merge pull request #496 from DavidWyand-GG/DamageFlashWhiteOut

Change default damage and white flash