jsMessage: Redesign in Vector/Monobook as bubble with auto-hide

jsMessage: Redesign in Vector/Monobook as bubble with auto-hide

A bit like the "Growl" notifications on Mac.

The message will auto-hide in all skins, which is especially useful
with VisualEditor because you it does most things through ajax which
means that a msg in there could be visible for way longer than it
should be with no way of hiding it.

By being designed as a floating bubble instead of a static positioned
element in regular document flow it also prevents the page flow
from being interrupted and moved down a bit. Again that was
especially annoying in VisualEditor because jsMessage forced itself
between the tab bar and the editor toolbar, which were meant to be
against each other.

Auto-hiding is disabled while the mouse if hovering the message.
The timer starts again when the mouse is no longer on it.

Also:
* cleaned up some whitespace issues in vector.js
* Removed jshintignore for skins/common
  Removed whitelisting of 'mw' global
  skins/common may not be prefect, but at least this way it gives
  warnings inside the code when writing/editing something, which is
  still useful.
  It helped to catch that 'mw' was used from the global scope.

Change-Id: I41c70d78c8ed8aeb91a598dc4a7b26dfad8d8f6c