Use blank nodes instead of _new_

[manishrjain]

mutation {
 set {
  <_new_:class> <student> <_new_:x> .
  <_new_:x> <name> "alice" .
 }
}

Nquads syntax allows to specify file/request-local IDs called blank nodes (bnodes). This is a standard approach, and I think it will be better to use them to auto-assign internal IDs:

mutation {
 set {
  _:class <student> _:x .
  _:x <name> "alice" .
 }
}

[ashwin95r]

Addressed with 046ace6.