When we load a Canto interaction but there's an identical existing interaction from BioGRID (or elsewhere?) we should just add the Canto details to the existing interaction. The details we should add are canto_session, curator_name, curator_email and date.
When we check for an existing symmetrical interaction we should check for an interaction annotated in the opposite direction too.
See also: [#426]
Related
Chado: #426
I've made the change to merge interactions and I'm running a load.