Use common field as index between CV and corpora data

[johngian]

Currently the CorporaCreator tool generates TSVs that don't have any common field to be used as index between CV database and Corpora database. In order to generate the diff we currently rename the clips path (to cleanup PII) and use that as a common field.

It would make things less complicated if:

• We keep the sanitized clip path in the CV database, or
• We keep the clip id in the CorporaCreator TSVs, or
• We don't store PIIs in the clip path so we could use it directly