And fix an error message typo

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The statistics module on the dashboard was using the incorrect query parameter
'stop'. This meant that the module was loading all tickets from the report start
date to the present day. This commit fixes this by using the 'period' parameter
instead.

  * Use the title of "Information" with internal tag of "info"
  * Add "Visibility" column to UI and retire "Required" and "Internal"
    columns
  * Add visibility selection to new fields and show visibility to the user
    information fields when displayed on the ticket details form
  * Make the visibility settings translatable
  * Use constants internally for visibility configuration detection
  * Use a larger input when managing the information HTML content
  * Fix validation errors for new fields
    * Enforce new field name uniqueness
    * Enforce new field name character validation

This is necessary to avoid confusion vs. closed state.

This allows fields to specify a visibility constraint that will be evaluated
in real time in the browser to automatically show and hide fields that
should be hidden based on values of other fields in the same form.

Validation is not performed on fields server-side if they are considered
invisible when submitted.

In some cases, a POST might be sent to the server and there be no draft. In
such a case, neither the draft nor the body of the page can be inspected for
images. Even worse, in some cases the previous images might be unlinked from
the article without being relinked. Therefore, the images will no longer be
linked to the page and will likely be purged from the system.

Show different messages and placeholder on ticket(s) deletions