Single-click insertion

Objectives:

* Reduce the number of clicks and mouse maneuvers required to insert
  media, references or template parameters
* Make use of highlighting with mouse movement or arrow key presses,
  similar to menus, to suggest action when clicked
* Improve the way media search results look and feel

Changes:

ve.ui.SelectWidget.js
* Add mouseleave handler to un-highlight when the mouse exits the widget
* Document highlight events (already being emitted)

ve.ui.SearchWidget.js
* Propagate both select and highlight events from results widget
* Make arrow keys change highlight instead of selection
* Get rid of enter event, make enter key select highlighted item instead
* Provide direct access to results widget through getResults method

ve.ui.MenuWidget.js
* Use the selected item as a starting point if nothing is currently
  highlighted when adjusting the highlight position

ve.ui.Dialog.js
* Add footless option to hide the foot element and make the body extend
  all the way down to the bottom
* Remove applyButton, which only some dialogs need, and should be creating
  themselves, along with other buttons as needed

ve.ui.Widget.css
* Change highlight and selected colors of option widgets to match other
  selection colors used elsewhere
* Leave selected and highlighted widget looking selected

ve.ui.Frame.css
* Add background color to combat any color that might have been applied to
  the frame body in the imported CSS from the parent frame

ve.ui.Dialog.css
* Add rules for footless mode

ve.ui.MWReferenceResultWidget.js,
ve.ui.MWParameterResultWidget.js,
ve.ui.MWMediaResultWidget.js
* Allow highlighting

ve.ui.MWParamterSearchWidget.js
* Switch from selecting the first item when filtering to highlighting

ve-mw/ve.ui.Widget.js
* Adjust media result widget styling to better match other elements

ve.ui.MWTransclusionDialog.js,
ve.ui.MWReferenceListDialog.js,
ve.ui.MWReferenceEditDialog.js,
ve.ui.MWMetaDialog.js
ve.ui.MWMediaEditDialog.js
* Add apply button, as per it being removed from parent class

ve.ui.MWTransclusionDialog.js,
ve.ui.MWReferenceInsertDialog.js,
ve.ui.MWMediaInsertDialog.js
* Insert parameter/reference/media on select, instead of clicking an
  insert button
* Use 'insert' instead of 'apply' as argument for close method

Bug: 50774
Bug: 51143
Change-Id: Ia18e79f1f8df2540f465468edb01f5ce989bf843