PDI-10396 - spoon splash screen overlay text has white background - used to be transparent

changed boolean flag to have transparent background
Merge pull request #392 from prakapenka/PDI-10396

PDI-10396 - spoon splash screen overlay text has white background - used  to be transparent
PDI-11427 - Integration test org.pentaho.di.core.plugins.PluginRegistryTest is unstable