(bug 45002) jQuery.valueview is now a single Widget using composition rather than inheritance

Before this change the standard jQuery.Widget inheritance mechanism was used to extend the
jQuery.valueview widget to make it suitable for all kinds of data value types. Now there is
only one single jQuery.valueview widget which is using so called valueview "Experts" which
take care over the handling of different data value types.
After this refactoring, only the String value is re-implemented. CommonsMedia will follow in
some follow-up, all other extensions using this will also require adjustments.

The following is a description of the new core components of jQuery.valueview:
* jQuery.valueview: Widget definition for displaying and editing data values. Each data value
  which should be supported by the valueview widget has to be implemented as a
  jQuery.valueview.Expert.
* jQuery.fn.valueview: jQuery widget bridge to instantiate a jQuery.valueview widget in the DOM.
* mediaWiki.ext.valueView: Object representing the "ValueView" MediaWiki extension.
* These first valueview expert is the "StringValue" expert. This one and all experts added in
  follow-ups can be found in jQuery.valueview.experts.<constructor-name>.
* other jQuery extensions required by this library which are not available in MediaWiki itself:
  - jQuery.eachchange
  - jQuery.inputAutoExpand
  These have been moved from the DataTypes extension as well.

Change-Id: If387a45e76b7aa6e8a0698b370d0e86c79fbad7d
Merge "(bug 45002) jQuery.valueview is now a single Widget using composition rather than inheritance"