Bulk mutations

[rmagen]

Solution suggestion

Optimize the Mutation steps to issue mutation UniQuerys with a bulk of Element, enabling the Controllers to issue bulk commands to the DB.

Questions

1. Should we enable bulk mutations directly from the UniGraph? That would entail adding on Tinkerpop's current Graph API.
2. Should changes be automatically committed to the DB after every query, or should we add a commit() method to UniGraph/Traversal?
3. Maybe using BulkLoaderVertexProgram, or a similar solution, would be a better choice?