Reuse methods from the wcw project

[iosonopersia]

Some functions related to external identifiers that can be found in the Pusher subproject of wcw could be reused inside the Identifier class of oc_ocdm.

They can be found here.

The key idea here is to provide a "validity check" functionality when the user tries to call methods such as create_isbn, create_issn and create_orcid.