Fixed Contributions Managers not showing due to MissingResourceException

There was no contributions field in the PDE.properties, which caused a MissingResourceException to be thrown each time a Tool/Mode/Library Manager was started. Further, we may need the title String, since each of the managers will need their entire title specified (since concatenating the type.getTitle() with " Manager" would no longer work, since, for example, in French, it would be written the other way around).