Show end timestamp

[tobiasKaminsky]

Sometimes we change only the end date of an existing event, e.g. from 6pm-8-pm to 6pm - 10pm.
Now it shows "a new event was created" and we wonder what happened.
With #12 it would show "an event was updated" and show "6pm-10pm" in the summary.

[tobiasKaminsky]

Also it is a nice enhancement for freshly created events, as then the other person directly see how long an event was planned.