No more confusing boolean argument for closing windows

window.close( true ) thing sucked, and was being named and used
inconsistently throughout the code.

The new approach uses an action string, so it looks more like
window.close( 'accept' ) or window.close( 'back' ). This makes it easy
to steer the behavior at any point in the window close code path.

Most importantly for the link inspector, this allows us to now restore
the previous selection when the user presses escape or clicks the back
button, while still moving the cursor to the end and collapsing the
selection upon pressing enter and allowing removal by clicking the
trash can.

This commit also cleans some things up, like the various ways we have
to close an inspector which all seem useless because we wouldn't want
to just randomly close an inspector on someone. An inspector should
be closed only when the user has dealt with it.

ve.InspectorAction.js
* Removed close method

ve.ui.LinkInspector.js
* Updated documentation
* Passing action to parent method
* Updated logic to deal with change from "remove" to "action" argument
* Added selection restauration on "back" action

ve.ui.Context.js
* Added action to call to close
* Removed closeInspector method

ve.ui.Dialog.js
* Moved event handlers to the top
* Added actions to calls to close
* Added click block event handler to prevent focus changes

ve.ui.Inspector.js
* Added actions to calls to close
* Added storing of previous selection - this is different from
  initialSelection because it's captured before the selection is
  modified by setup

ve.ui.Window.js
* Updated documentation
* Updated argument name from "remove" to "action"

ve.ui.WindowSet.js
* Updated documentation
* Removed auto-close, replaced it with error if trying to open a window
  when another is already open
* Removed close method

Change-Id: Ie8f72504177dd6ba169fdddbb776fd5397b831c4
Dialog button changes

ve.ui.MetaDialog.js
* Added scrolling to outline panel

ve.ui.css
* Added reusable animation keyframes

ve.ui.Dialog.css
* Changed dialog head style
* Changed dialog cancel button to close icon button
* Added animation of dialog opening
* Increased min-height of dialog to always show a little content

ve.ui.Icons-*.css
* Added close icon (not sure why it was missing)

ve.ui.Window.css
* Moved head padding out of window and into implementations of window

ve.ui.Dialog.js
* Moved apply button to footer
* Renamed cancel button to close button
* Overrode close method with triggers a closing animation and then calls the parent close method after an animation is complete
* Added classes to close and apply buttons to make styling less ambiguous
* Converted cancel button (now the close button) to an icon button

ve.ui.Window.js
* Added footer to dialog

VisualEditor*.php
* Added close message

Change-Id: Iededbc54b287328b3047b05efad6ca3cc152caa5