code: protected void installExtension(ExtensionId extensionId, String namespace, DefaultExtensionPlanTree parentBranch)
          throws InstallException
      {
          installExtension(extensionId, false, namespace, parentBranch);
      }
docs: Install provided extension.
  
  @param extensionId the identifier of the extension to install
  @param namespace the namespace where to install the extension
  @param parentBranch the children of the parent {@link DefaultExtensionPlanNode}
  @throws InstallException error when trying to install provided extension