Add attributes to existing entities/relations

[hkuich]

Given already existing entities/relations in your graph, do match/insert to add attributes:

match $entity isa entity, has identifying-existing-attribute "read from data table with new attributes";
insert $entity has new-attribute "read from data table with new attributes", has new-attribute-2 "...", ...;

Will need to adjust processor and data config and a new query builder.

[hkuich]

implementation complete - merge request coming