Add #compareTo to ve.dm.Annotation

We have a compareTo function AnnotationSet, but not for
single annotations.

Change-Id: I8858715133ff657526fc12c21dff151b14fe795b
LanguageInputWidget rewrite

* Move fields into OO.ui.FieldLayout's and remove most of the
  custom styling.
* Fix various bits of documentation.
* Convert properties back to local variables where not re-used.
* Simplify API so that the widget deals primarily with annotations.
  Remove #getValue and replace #setValue with #setAnnotationFromValues.
* Replace setTimeout debouncing with an 'updating' state flag.
* Remove 'Change language' from i18n as only used in MW.
* Inline 'initialize' into constructor.
* Remove initial values from config, never used.

Change-Id: If121603b5637eae72a4637197c6fcc94c1bc4c4a
Merge "Add #compareTo to ve.dm.Annotation"
Merge "LanguageInputWidget rewrite"