Made Edges/EdgePopulation get functions more consistent

[joni-herttuainen]

Old behavior

Edges.get:

• return the query as is if properties is None
• properties is optional (defaults to None)

EdgePopulation.get:

• return resolved ids if properties is None
• require properties to be defined in the function call

New behavior:

Edges.get / EdgePopulation.get:

• return resolved ids if properties is None
• properties is optional (defaults to None)