Enable to import both Avram and "Yale" format of schema files

[pkiraly]

This is needed for the inclusion of #371.

[nichtich]

No need to do so, as the Yale format is being changed to comply to Avram specification.

[nichtich]

Is class YaleMarc21SchemaReader still used? As far as I understand, both the class and src/main/resources/marc/authority-schema.yale.json are only used in test class YaleMarc21SchemaReaderTest but not on production, so they can be removed?

[pkiraly]

The analysis based on the authority schema is not yet in production, but only used in test classes (following a test driven development version). I think you are right, the YaleMarc21SchemaReader could be removed shortly.