Add date-like processing

Add processing methods which go through a given string,
looking for date indications, and returning it as an {{Other date}}.
Add unit tests for every covered case.
Add post-processing to the upload process

We want to process some fields to enrich metadata on the fly.
Here we enrich the 'Format' field with itself, and enrich the 'Date'
and 'Year' with the 'Analyse' field.