message: changes to support $.propname syntax for trigger mappings
diff: @@ -436,6 +436,7 @@ export class MapperService {
  let expressionHead = '';
  let expressionTailParts;
  const resolver = root.data.rootType;
  + const nodeName = root.data.nodeName;
  const makeResolvable = expr => '$' + expr;
  if (resolver === ROOT_TYPES.TRIGGER || resolver === ROOT_TYPES.ERROR) {
  @@ -448,9 +449,11 @@ export class MapperService {
  expressionHead += propName ? propName.data.nodeName : '';
  expressionHead = makeResolvable(expressionHead);
  expressionTailParts = nodes.slice(2);
  + } else if (resolver === ROOT_TYPES.FLOW) {
  + expressionHead = makeResolvable(nodeName);
  + expressionTailParts = nodes.slice(1);
  } else {
  - const nodeName = root.data.nodeName;
  - expressionHead = resolver ? makeResolvable(nodeName) : nodeName;
  + expressionHead = nodeName.indexOf('$') === -1 ? '$.' + nodeName : nodeName;
  expressionTailParts = nodes.slice(1);
  }
  return[expressionHead].concat(
  