Add convenient assertion methods for revision, quotation, primary source, mention & influence records

[cdboer]

In release 1.1.0 convenience methods for assertions like derivations (ProvEntity.wasDerivedFrom) where added that allow the following syntax:

graph = ProvDocument()
e1 = graph.entity("e1")
e2 = graph.entity("e2")
e1.wasDerivedFrom(e2)

For other assertions, like the ones mentioned in the title, these methods don't exist yet. If you wanted to add a revision record to the initial example you'd have to use the ProvBundle.wasRevisionOf method like this:

graph = ProvDocument()
e1 = graph.entity("e1")
e2 = graph.entity("e2")
e1.wasDerivedFrom(e2)
# e1.wasRevisionOf(e2) doesn't exist
graph.wasRevisionOf(e1, e2)

I think adding convenience methods for these assertions would improve readability.

Candidates for such convenience methods:

• ProvEntity.wasRevisionOf
• ProvEntity.wasQuotedFrom
• ProvEntity.hadPrimarySource
• ProvEntity.mentionOf
• ProvEntity.wasInfluencedBy
• ProvAgent.wasInfluencedBy
• ProvActivity.wasInfluencedBy