Propagate icon definition from library or graph

It is very useful to be able to propagate the icon definition from
library to component/node. Moreover, inports/outports icon should
be overridden by the graph def.
Fix group css color

When a group is not selected, its css class giving its background
color should range from 1 to 10.
Enable SVG icon to be loaded

If a property iconsvg is set into the node or the component loaded
via the library, iconsvg value will be used as a URI and a tag
<g><image xlink:href="{{this.props.iconsvg}} ..../> will be created
Fix jshint errors

Add missing semicolons
Change '!=' to '!==' to compare with ''
Merge pull request #178 from lhausermann/master

icon propagation / group color fixes, svg <image> hack