Modify styles, add disabled and read-only for widgets

demos/ve/demo.css, demos/ve/index.php
* Style changes for utilities and dump output
* Initially disable the log range button, activate when there's a range to log
* Make range inputs read-only
* Rename some widget variables
* Add extra structure and classes to dump output

ve.ui.Widget.css
* Remove left/right margin for buttons
* Simplify opaque white color
* Modify selector for disabled buttons - see changes in ve.ui.Widget.js
* Added styles for text input widget's readonly and disabled states

ve.ui.Widget.js
* Added disabled state

ve.ui.ButtonWidget.js
* Moved click event handler to method

ve.ui.InputLabelWidget.js
* Moved click event handler to method

ve.ui.InputWidget.js
* Moved input change event handler to method
* Added readOnly state

ve.ui.LinkTargetInputWidget.js
* Corrected documentation

ve.ui.MenuWidget.js
* Blocked interaction while widget is disabled

ve.ui.MWLinkTargetInputWidget.js
* Corrected documentation
* Blocked interaction while widget is disabled

ve.ui.TextInputMenuWidget.js
* Blocked interaction while widget is disabled

Change-Id: I7ea89873b50a98d058d1dd1e309e3e8b7c8e7b2e
Merge "Modify styles, add disabled and read-only for widgets"