New navigator options:
* @property {Boolean} [showNavigator=false]
* Set to true to make the navigator minimap appear.
*
* @property {Boolean} [navigatorId=navigator-GENERATED DATE]
* The ID of a div to hold the navigator minimap.
* If an ID is specified, the navigatorPosition, navigatorSizeRatio,
navigatorMaintainSizeRatio, and navigatorTop|Left|Height|Width options
will be ignored.
* If an ID is not specified, a div element will be generated and
placed on top of the main image.
*
* @property {String} [navigatorPosition='TOP_RIGHT']
* Valid values are 'TOP_LEFT', 'TOP_RIGHT', 'BOTTOM_LEFT',
'BOTTOM_RIGHT', or 'ABSOLUTE'.<br>
* If 'ABSOLUTE' is specified, then navigatorTop|Left|Height|Width
determines the size and position of the navigator minimap in the viewer,
and navigatorSizeRatio and navigatorMaintainSizeRatio are ignored.<br>
* For 'TOP_LEFT', 'TOP_RIGHT', 'BOTTOM_LEFT', and 'BOTTOM_RIGHT',
the navigatorSizeRatio or navigatorHeight|Width values determine the
size of the navigator minimap.
*
* @property {Number} [navigatorSizeRatio=0.2]
* Ratio of navigator size to viewer size. Ignored if
navigatorHeight|Width are specified.
*
* @property {Boolean} [navigatorMaintainSizeRatio=false]
* If true, the navigator minimap is resized (using
navigatorSizeRatio) when the viewer size changes.
*
* @property {Number|String} [navigatorTop=null]
* Specifies the location of the navigator minimap (see
navigatorPosition).
*
* @property {Number|String} [navigatorLeft=null]
* Specifies the location of the navigator minimap (see
navigatorPosition).
*
* @property {Number|String} [navigatorHeight=null]
* Specifies the size of the navigator minimap (see
navigatorPosition).
* If specified, navigatorSizeRatio and navigatorMaintainSizeRatio
are ignored.
*
* @property {Number|String} [navigatorWidth=null]
* Specifies the size of the navigator minimap (see
navigatorPosition).
* If specified, navigatorSizeRatio and navigatorMaintainSizeRatio
are ignored.
Fixes#280 and #296
