Query function rework

[m-appel]

This PR reworks the main functions used to query/create nodes. Both get_node and batch_get_nodes functions now have a similar interface and behavior. Added support for multi-label nodes.

• batch_get_nodes_by_single_prop
  • Renamed from batch_get_nodes
  • Added create parameter for consistency
• get_node
  • Change default value of create parameter to True. There was no instance where this function was called with create=False and now it is consistent with batch_get_nodes.
  • Change interface to be the same as batch_get_nodes.
  • Id properties used as the search predicate must now be specified explicitly instead of being inferred from constraints.
• batch_get_nodes
  • New function that supports querying/creating nodes with multiple properties, where as subset of the properties can be used as the search predicate.
• batch_add_node_label
  • New function to add additional labels to existing nodes.
• batch_create_nodes
  • Deleted due to inflexibility and danger of creating duplicate nodes.

[romain-fontugne]

I tried and it seemed to have worked as expected. thanks!

[romain-fontugne]

ah, I think the version I tried didn't have the constrains and indexes. I'll try again before merging

[romain-fontugne]

Looks good to me, thanks!