remove subgroup from subgroups list if there is no more items in the …

Added option zoomKey

see #909

Added feature that allows the border for a circularImage shape to be dashed

Changed shapeProperties.borderDashes type description from "Object or Boolean" to Array or Boolean".
Merged circularImageWithDashedBorder example into shapesWithDashedBorders example.
Added enableBorderDashes and disableBorderDashes function calls to Database.js, Ellipse.js and Box.js, to enable/disable dashed borders.

Don't change backgroundColor if not requested on setOptions

Replaced dashes property in options.js with a shapeProperties object containing a borderDashes property.
Replaced dashes property in defaultOptions in NodesHandler.js with shapeProperties object having its borderDashes property set to false.
Created implementations of enableBorderDashes and disableBorderDashes functions in NodeBase.js
Updated CircleImageBase to use enableBorderDashes and disableBorderDashes for enabling/disabling dashed borders.
Added to ShapeBase enableBorderDashes and disableBorderDashes calls to allow all shapes that have borders to have the dashed borders feature.
Updated example demonstrating how to apply the dashed border to a circularImage node
Created example demonstrating how to apply the dashed border to a all shapes that support dashed borders.
Updated documentation explaining the usage of the shapeProperties.

Missed "apply" call on DOMtoCanvas method

Added the following:
- dashes property to nodes in options.js
- dashes property with value false to defaultOptions in NodesHandler.js
- support for Arrays to selectiveNotDeepExtend function in util.js
- functionality to CircleImageBase.js that allows circularImage nodes to have dashed borders
- example demonstrating how to apply the dashed border to a circularImage node
- documentation explaining the usage of the dashes property on a node

Missed "apply" call on DOMtoCanvas call