code: boolean registerAddOn(AddOn pAddOn) {
          if (!mRegisteredAddOns.containsKey(pAddOn.getAddOnId())) {
              mRegisteredAddOns.put(pAddOn.getAddOnId(), pAddOn);
              if (pAddOn.hasConfiguration()) {
                  addConfiguration(pAddOn.getAddOnId(), pAddOn.getConfigurationPane());
              }
              LOGGER.info("The add-on " + pAddOn.getAddOnId() + " has been registered.");
              return true;
          } else {
              LOGGER.warn("The add-on " + pAddOn.getAddOnId() + " is alreadry registered.");
              return false;
          }
      }
docs: Registers the add-on. If the add-on is not loaded, loads it.
  
  @param pAddOn The add-on to register.
  @return <code>true</code> if the add-on is successfully registered.