feature(annotations): add ES7 decorator functions

[L8D]

[ghost]

I think the decorators should also be exported from the index.js. Otherwise it works great. Thanks.

[Pajn]

Any update on this? Would need this.

I had to change line 33 in util.js from
var ownKeys = (this.Reflect to var ownKeys = (Reflect for it to work, but that seems to be an older thing.

[L8D]

This is now broken as the proposal has changed slightly. The new signature is (target, name, descriptor) so we'd need to annotate descriptor.value if a decorator is applied to a factory function instead of a class.