* Added getBaseEdge, getClusteredEdges updateEdge and updateClusteredNode to allow option changes of the clustered edges as they are no longer the original base Edge

changing edge color is a good example.
i.e network.clustering.updateEdge(originalEdge.id, {color : '#aa0000'});
will now update all edges including the ones that were created when clustering.

Also when clicking on a clustered edge the event returns the clustered Edge id, which doesn't mean a lot.
This can be now converted back into the original edge with
network.clustering.getBaseEdge(clusteredEdge.id)

Similar with updateClusteredNode
This new method allows the options to be changed on a clustered Node.

i.e clicking on a clustered node gives its clustered node id.
Want to change the clustered image to a star then do this
 network.clustering.updateClusteredNode(clusteredNodeId, {shape : 'star'});

* Updated docs with getClusteredEdge, getBaseEdge, updateEdge and updateClusteredNode

Also added method subsections into contents

* Added better error handling to updateEdge and updateClusteredNodes

corrected errors spotted by @mojoaxel

* Added example html demonstrating getBaseEdge, getClusteredEdges updateEdge and updateClusteredNode

code cleanup;

Add flag to check whether an item in the Itemset is currently being dragged

Perturbing the nodes was being performed on all nodes regardless of whether they were set as fixed.

Added a "showLegend" option which can be used to toggle legend drawing
Added legend drawing to 11_tooltips and to playground examples
Added description of showLegend option to documentation

Signed-off-by: André Martins <aanm90@gmail.com>

It was broken by PR (#1729), which fixed issues #112 & #1730.
As far as I can tell that change shouldn't influence the DataAxis (vertical-axis), but only the horizontal axis.

 @yotamberk can you check if your examples still work as expected?

As the documentation on vis.js nodes can be styled with align: left|center

allOptions does not include this option and throw an error on option validation.

- Added interpolation option for interpolation of images, default true.

Internet Explorer does not support the ES6 Number.parseFloat (see http://caniuse.com/#feat=es6-number). Instead, substitute the regular parseFloat method.

- Added parentCentralization option for hierarchical layout.