Adds file links to the project as added by PM.

Adds file links to the project as added by PM. The following properties can be specified for each file link:<ul><li>url (required, 400 Bad Request is returned otherwise)</li><li>category (required, 400 Bad Request is returned otherwise)</li><li>languageIds – when the file category depends on a list of languages</li><li>languageCombinationIds – when the file category depends on a list of language combinations</li></ul>