Conflict/Overlap Checker

[Simon-Laux]

Have some sort of Mechanism that checks for overlapping entries and offer to fix them.

Overlapping entries should not happen, but they can happen and thus we should have something to notify the user about the problem and give them an easy way to resolve it. be it allowing easy editing or an automatic method of solving it (last entry end time gets replaced by next entries start time, if it is bigger than the start time?).