[Bookmark] Add JS bits of bookmark

This add the Bookmark extension and its JS public API. It is implemented on top of an in-memory fake "bookmark provider". The next step will be to replace that fake provider with a real one that asks the native code for information, that will use native API in `favorites.h`.

All the API related details covered by TCT are already being handled. In fact, except for tizen.bookmark being read-only (to be handled in Crosswalk), all the TCT tests should pass.

See commit messages for details.