Editing existing datasets via MDE

[matamadio]

The current approach to edit an existing dataset involve downloading+editing the json and then pushing a new PR.
It would be great to enable an "edit dataset" function which allow to do it via the MDE directly.

Postponed after:

• RDLS reaches v1.0

[matamadio]

Connected with naming convention: see #114 (comment)
MDE should check existing ids/filenames in JKAN in addition to reactive validation done by JKAN CI.