Method: Remove the difficulties created by the `create_difficulties()` function

Method: Handle form submission of update related actions

Method: Stores an admin notice for the current state of the background updater

Method: Create basic course difficulties on installation

Method: Update the LifterLMS DB record to the latest version

Method: Create files needed by LifterLMS

Method: Update the LifterLMS version record to the latest version

Method: Store all default options in the DB

Method: Redirects users to the setup wizard

Method: Create essential starter pages