Add the ability to bind node locations to properties

[yGuy]

Just like for the underlying widget, where you can bind the location (x/y) and size to your data, this should also be possible using convenience mappings to neo4j node properties.

I guess that with the next major release heatmap and geo data will be supported, too, but this is not about geo-data, only, but for simple x/y bindings that are not geo coordinates.