* FEATURE: Import into `category_users` table
* FIX: Failed to import `user_options` unless `timezone` was set
* FIX: Prevent reusing original `id` from intermediate DB in `user_fields`
* FEATURE: Order posts by `post_nuber` if available
* FEATURE: Allow `[mention]` placeholder to reference users by"id" or "name" (username)
* FEATURE: Support `[quote]` placeholders in posts
* FEATURE: Support `[link]` placeholders in posts
* FEATURE: Support all kinds of permalinks and remove support for `old_relative_url`
* PERF: Speed up pre-cooking by removing DB lookups
Notable changes:
* Imports a lot more tables from core and plugins
* site settings
* uploads with necessary upload references
* groups and group members
* user profiles
* user options
* user fields & values
* muted users
* user notes (plugin)
* user followers (plugin)
* user avatars
* tag groups and tags
* tag users (notification settings for tags / user)
* category permissions
* polls with options and votes
* post votes (plugin)
* solutions (plugin)
* gamification scores (plugin)
* events (plugin)
* badges and badge groupings
* user badges
* optimized images
* topic users (notification settings for topics)
* post custom fields
* permalinks and permalink normalizations
* It creates the `migration_mappings` table which is used to store the mapping for a handful of imported tables
* Detects duplicate group names and renames them
* Pre-cooking for attachments, images and mentions
* Outputs instructions when gems are missing
* Supports importing uploads from a DB generated by `uploads_importer.rb`
* Checks that all required plugins exists and enables them if needed
* A couple of optimizations and additions in `import.rake`
