Ghost: Add Player GhostTrack of the user

[fwild]

It should be possible to record the GhostTrack of what the learners do in an ARLEM experience.

This recorded data cannot be stored with the ARLEM zip, as it logically is formative assessment data - akin to xAPI logs. A neat solution might be to store the GhostTracks into Moodle and then link the URL of the data file to an xAPI statement.

An idea for how to embed this in the UI could be to either add a Ghost to the action step and add a "[X] user generated content" to its edit panel, or to add a config option to the action step itself that specifies "[X] log user ghost track".

The user generated content idea is captured more generically for all augmentations here: #469