Disable sameAs automatic node merging by default

[timbl]

https://github.com/linkeddata/rdflib.js/blob/master/src/store.ts#L198

sets the default mode for a Store to implement 'smushing' of nodes together in the graph. This is not something standard functionality, and may confuse future developers.

These features were used in the mashlib when it was used in the old says of 'mashups', to when combining data from many trusted open data sources, like the network of FOAF files. In fact the FOAF ontology specifically identify people by having the same properties, such as same email address or hash or email address.

But nowadays in the solid world, the data is from different resources has very different trust and this technique is not so appropriate. Anyway it is I think reasonable to expect devs in future who want to use the features to turn them on explicitly.

This is formally a breaking change to the API though I doubt many people even know about the features. This will of improve RDF/JS compatibility.

[timbl]

Fixed by #492