Added functionality to extend the fields array, to a fields object,
similar to the type declaration. This makes it possible rename
properies when you get them.

- Added option to bypass default groups. If more groups are specified in the nodes than there are in the groups, loop over supplied groups instead of default.
- Added two new static smooth curves modes: curveCW and curve CCW.
- Added request redraw for certain internal processes to reduce number of draw calls.

Add the ability to use icon fonts for nodes such as FontAwesome

- Added fontSizeMin, fontSizeMax, fontSizeMaxVisible, scaleFontWithValue, fontDrawThreshold to Nodes.
- Added fade in of labels (on nodes) near the fontDrawThreshold.
- Added nodes option to zoomExtent to zoom in on specific set of nodes.
- Added stabilizationIterationsDone event which fires at the end of the internal stabilization run. Does not imply that the network is stabilized.
- Added setFreezeSimulation method.
- Added clusterByZoom option and increaseClusterLevel and decreaseClusterLevel methods.

Still clustering bug and need more documentation on new features