Implement add reference #2
Description
Requirements:
- It should be possible to source every statement added
- Adding a reference should be possible for single statements as well as groups of statements
- References must be tied to unique identifiers for the purposes of querying them
- A group of statements (a graph) with distinct references need not be tied to the same graph name
- Data pulled from either Pubmed or Wormbase should be identified as such in the database.
- Identification must be on the identifier for the reference.
- Additional data sources must follow the same structure