Introduce UIToolbox class
Add styleNode method
Add constructor in UIToolbox to init SpriteManager
Change styleNode to public static
Add and remove Sprite methods
Add cloneGraph to unused class and comment it
Description of UIToolbox class
Cleanup Louvain class
Rename local variable e so it doesn't hide the field
add clone method in Utils

Copied from the latest nightly build of gs-core (should be dropped when
updating to gs-code 1.3 and use Graphs.clone(Graph graph) instead).