code: function DirectiveContext(strategy, expression, arrayPath){
    this.resolved = false;
    this.strategy = strategy;
    this.expression = expression;
    this.path = arrayPath;
    this.sympath = treeUtils.joinPaths(arrayPath);
  }
docs: Represent the context needed to resolve a directive.  This should be returned by the directive to the callback.
  If the directive has resolved the value, there is a convenience method "resolve" you can call to set the value
  and transition the completion state to "resolved".
  @param strategy {String} name of the directive.
  @param expression {String} the value after the directive in the expression
  @param arrayPath {Array} path to the leaf in which the directive was declared.
  @constructor