provide alter hooks for modifying default behaviors

adding some API flexibility would be key for integrations with different workflows. For example in ELMSLN we have many systems which students engage with but don't realize they are or are things they don't actually have an account on (like a video being served up in a frame / interaction being loaded remotely and embedded in a page). In this instance, tracking the page isn't the important part, but the interaction / seeing the media could be (which is from another system where they are anonymous).

Using some minor API flexibility we could allow tracking of anonymous users on these other locations, yet modify the XAPI statement just prior to sending off to the LRS and append properties about the user that we know even though they aren't logged in (this is possible with cookies and single sign on systems which are pervasive yet not necessarily being utilized at the Drupal layer for a "user" account).

patch for a few of these where they make sense soon I hope.