update npm package "harmony-reflect" to v1.1.0
update objrefProxy w.r.t. latest ECMAScript 6 draft

* update objrefProxy traps according to r27 of the ECMAScript 6th
  edition draft (resp. harmony-reflect v1.1.0)
* name all trap functions for better stack traces
* add unit tests for "has" trap
* improve existing unit tests to better mimick the distinction between
  objref and actual object