An admin to publish mdims and set the publication slug

[rakyi]

• Table view with a list of mdims, with columns:
  • (Optional) Thumbnail of the default view
  • Title (with a link to preview)
  • ETL path - needs a new column in the DB (make mandatory eventually in both API and DB), coordinate with Mojmir
  • Editable slug
  • Button(s) to publish/unpublish
  • (Optional) published at (change existing column to be a date)
  • (Optional) updated at
• Validate slug uniqueness
  • Across mdims
  • Across normal graphers
  • Across grapher redirects
  • Add the same, but in reverse, to the chart admin