code: public Extensions create(FeatureTable featureTable) {
  		return create(featureTable.getTableName(), featureTable
  				.getGeometryColumn().getName(), featureTable.getPkColumn()
  				.getName());
  	}
docs: Create the RTree Index extension for the feature table. Creates the SQL
  functions, loads the tree, and creates the triggers.
  
  @param featureTable
  feature table
  @return extension