deposit: adaptation to fieldlist separation

After appling commits below to invenio. These one needs to be applied to inspire.

Invenio commits to apply:
https://github.com/kneczaj/invenio/commit/764aa0fdd67e8e8fd724fb47309c29aa912e563f
https://github.com/kneczaj/invenio/commit/7afdb11eb45f620522e74e2281e60e7dd889e31a
https://github.com/kneczaj/invenio/commit/a858d9b6648fa394d0ce8edcde49c728a8260cce

Our sprint-2 branch commit, which is incompatible - to remove:
https://github.com/jmartinm/invenio/commit/d7d8dd804c7911afc23501fa700d0ac60f543377