Bug 837494 - re-implement `contentStyle*` using the new nsIDOMWindowUtils methods

- added Irakli's Method library
- added `mod` module, with `attach`, `detach` and `getWindowTarget`
- "unfreeze" classes in heritage - it fixes bug 827400 too
- added `loadSheet` and `removeSheet` to window/utils
- added `values` method to util/object
- replace usage of stylesheet services with `attach`/`detach` a `Style` object