Wikivoyage migration/Accounts

Current WV Accounts

 * Shared user table for de/it
 * Split user tables for the rest
 * Users are being asked if they want to opt-in to migrating accounts
 * Many prefixed "accounts" / edits from imported content for attribution
 * pseudo user pages in the User: namespace without actual users

Migration

 * exclude any user information where we don't have the account transfer agreement)
 * rename accounts that don't have account transfer permission to (WV-whatever)
 * setup title blacklist rule for special prefixes
 * Special:GlobalUsers doesn't show any conflicting usernames currently
 * After migration, we will prevent users from taking any action if not attached to CentralAuth