* WIP Implement polymorphic sitetree link tracking
* Update unit tests
Merge SiteTreeTrackedPage into SiteTree directly
* Fix bugs and issues
* Fix support for file link tracking
* Add missing use
* Add back deprecated extension
* Remove obsolete belongs_many_many
* Update deprecations
* BUG Ensure non-SiteTree records support link tracking
* Safer changed check
* Shift file tracking test to assets module
* Better check for live stage on versioning
* Deprecate method
* Cleanup virtualpage
* Clear records on delete
* Ensure upgrade task occurs on draft
* fix linting
Damian Mooyman