Analytics needs rethinking

[robert-belleman]

The current "analytics" functionality records events as they occur during a session; as described in section 4.2.2 of Emil van Veen's thesis): "1) the start and end of a timeline, 2) the start and end of a scenario, 3) the start and end of a scene, and 4) the occurrence of a key interaction moment". The problem is that the records that are produced are not "ACID" structured, which makes robust analysis hard. For example: "start" and "end" events of a timeline, scenario or scene are not always balanced (i.e. there is no matching "end" with every "start", which can happen when a client is interrupted). It is also difficult to tell apart sessions and interaction, which is wanted in the dashboard by Sharon Monk.