create an INITIAL workflow status

[DonHaul]

Currently once a new workflow is created it is set imediately to RUNNING.
This can be misleading as the workflow can be in a queue for sometime before its actually picked up.

as such I propose we create this new INITIAL state, similar to how we have it in the current holding pen.

https://github.com/inspirehep/inspirehep/blob/master/backoffice/backoffice/authors/constants.py#L21

[drjova]

Created Processing status inspirehep/inspirehep@8bb2a6a