implement event consumption

[BBortfeldt]

Problem
Currently signals that are used to compose an aggregated event (e.g. MoveEvent) are not removed from the list of events. Therefore these can be used to aggregate another event. This can lead to a magnitude of false events which only increase the more events are in the event window of the cep system.

Solution
Signals that were used to aggregate a new event should be removed form the list of available events. There are several possibilities.

The best would be to remove the events from the Esper event list and therefore can not be used again in the aggregation of another event. It is currently not known if this is possible and must be analysed. If it is possible this would be the optimal solution.

A fallback solution would be to implement a time window. Then events only "live" for a certain amount of time or only events that occur within a specified timeframe would be used to aggregate a new event. This can be implemented in Esper but can lead to problems depending on the timeframe.