Consider splitting up and/or renaming post_zephir_processing

[aelkiss]

This is once again something that does multiple things.

We might want to consider:

• extracting only the stuff that is based around rights somewhere else ("rights_processing"?) -- that's mostly perl, and it is concerned with generating rights, loading rights, and adding rights info to catalog records.
• extracting the verification functionality to a "metadata_verifier"
• putting any common ruby stuff in a gem??
• laying the "post-zephir processing" name to rest