Get GraphEntity properties map

[jkxplg]

Hi,

Thanks for this project!

When running a query and getting a node/edge in the response, there is no way of iterating over all the properties. This might be useful when I'm not interested in a set of particular properties but rather in all properties.
I think that exposing the properties map (or at least the keys) should solve this.

[DvirDukhan]

@jkxplg property names are now available. Note that this snapshot's package structure is a bit different than the previous commit so you might need to adjust.