code: function _keySourceHintFrom( method, source, environment ){
  		var hints = [];
  		if( method ) hints.push( method );
  		if( source ) hints.push( source );
  		if( environment ) hints.push( "WHEN " + environment );
  
  		return hints.join(' ');
  	}
docs: construct a source hint for the ConfigStore
  Hints are stored in the config to indicate source of applied changes
  
  @param method
  @param source
  @param environment
  @return {string}
  @private