cubicweb-vcsfile #1777404 fix VersionedFile dc_long_title (+ improve its i18n) [resolved]

It was previously using a non-world-readable attribute and its i18n string was incorrect english.

See proposed changeset d766989873cd of https://bitbucket.org/fcayre/vcsfile

prioritynormal
typebug
done in1.8.7
load0.100
load left0.000
closed by#831a676d1336 closes #1777404: improve VersionedFile dc_long_title msgid