Prepare DLFileRank entity for the new staging environment

In order to use the DLFileRank in the new staging environment certain modifications has to be performed on the entity.

These modifications are:

• make it a proper audited model (few columns were missing, some audited model columns were there)
• add UUID
• the two upper will make this a staged model

The service implementation has to be modified accordingly, and an upgrade process should be written as well.