Generic language inspector

* Remove ULS dependencies
* Use toggle widget for direction
* Make AnnotationInspector more configurable, and be able to add to
  insertion annotations when used on a zero-length selection
* Make language annotations apply to appended content
* Allow language inspector for pre-annotation
* Cleanup API of language widget to be annotation-oriented
* Use new ButtonOptionWidget

Change-Id: Ie74d98283c2b2fdd2d6070f6a5f69d2d39d41aaa
Merge "Generic language inspector"