Incomplete data: replace red shadow

[djohs]

We discussed to replace the red shadow, wich is displayed on nodes with incomplete data, with an exclamation mark icon. This is trivial but doesn't look convincingly:

Unfortunately vis.js doesn't offer a possibility to color the text of a node individually or show a icon additional to the node. There is a possibility to embed HTML into a SVG-Tag and add this to the image attribute of the node (http://visjs.org/examples/network/nodeStyles/HTMLInNodes.html). But this approach is very performance intense and probably also not cross-browser stable.

Proposals:

• We don't replace the red shadow or search for another possibility to highlight the nodes with vis.js (possibilities are border color, fill color and shadow)
• We use the exclamation mark icon showed in the screenshot above.
• We patch vis.js to represent icons next to a node