SPI to add @Option Converters for custom types

   void init(@Observes final Startup event, final PluginCommandCompleter pluginCompleter) throws Exception
   {
      BooleanConverter booleanConverter = new BooleanConverter();

      addConversionHandler(boolean.class, booleanConverter);
      addConversionHandler(Boolean.class, booleanConverter);
      addConversionHandler(File.class, new FileConverter());
      addConversionHandler(Dependency.class, new DependencyIdConverter());
      addConversionHandler(URL.class, new URLConverter());
      ...
   }

public interface OptionValueConverter<T> {

   public boolean supports(Class<?> type);

   public T convert(Object value);

}