This PR improves the implementation of the BioRed corpus:
In the previous implementation a unique entity was created per entity mention and database identifier. This was fixed to a single entity mention having multiple database ids.
Furthermore, the name of the database a entity is linked to was added
BioRed only provides abstract-level annotations for entity-linked relation pairs rather than materializing links between all surface form mentions of relation. Analogous to BC5CDR we enumerate all mention pairs concerning the entities in the triple.
This PR improves the implementation of the BioRed corpus: