Bludit v4.0.0 - Release candidate 3

• Add information about the "admin panel" in the welcome pages
• Delete the upload directory when the page is deleted, thanks @emanueleg
• Create the upload directory for welcome pages, thanks @emanueleg
• Add pages preview, missing feature from v3, thanks @emanueleg
• Add delete user, missing feature from v3, thanks Tim Moritz
• Update the Italian dictionary, thanks @eagleman
• Add missing environment variables for the Installer
• Validate JSON format when the user define custom fields
• Disable autocomplete feature for form inputs #1430
• Remove HTML entities for auto URL generated #1428
• German dictionary updated, thanks @clickwork-git
• Fix for Blog URL filter, #1370
• Change order for more options, #1423