code: public CapsuleLauncher setProperty(String property, String value) {
          if (value != null)
              properties.setProperty(property, value);
          else
              properties.remove(property);
          return this;
      }
docs: Sets a property for the capsules created by {@code newCapsule}
  
  @param property the name of the property
  @param value    the property's value
  @return {@code this}