code: void startBlockImpl( String[] selectors ) {
          for( int i=0; i<selectors.length; i++ ) {
              if( i > 0 ) {
                  output.append( ',' );
                  newline();
              }
              insets();
              append( selectors[i] );
          }
          space();
          output.append( '{' );
          newline();
          incInsets();
      }
docs: Output a new block and increment the insets.
  
  @param selectors the selectors of the block.