core/lib/reflect.js: removed patching of __proto__

setting __proto__ after patching it reflect.js (look at the direct
function application for var __proto__setter), caused "TypeError:
Generic use of __proto__ accessor not allowed"

for now, we should use
  Object.setPrototypeOf(target, newProto)
instead of
  target.__proto__ = newProto
for awareness of proxies and non-extensible objects
core/lib/reflect.js: updated harmony-reflect to 0.0.7

fixes the problem mentioned in 752f342f2dea43ce05c583f363d8b3fc6d8c4a9d,
see github.com/tvcutsem/harmony-reflect/issues/18 for details
Object Versioning: initial tests + naive proxies + data structure
Object Versioning: refactored initial proxying and data structure
Object Versioning: hopefully better understandable tests