`TimeSeriesSource`: get activation ticks

[sebastian-peter]

As discussed in ie3-institute/simona#98 (comment), the interface and corresponding implementations of edu.ie3.datamodel.io.source.TimeSeriesSource should be enhanced with a method that returns all activation ticks for a time series (after a given time):

List<ZonedDateTime> getTimeKeysAfter(ZonedDateTime time);

This way, the implementations can take into account efficient methods for each data source type (e.g. with SQL this can be solved with a simple and quick query).

[sebastian-peter]

Possibly a duplicate of #506