add implicit Successible and Predecessible for Timestamp

Add implicit Successible and Predecessible for Timestamp, so the toLeftClosedRightOpen method is avaliable for Interval[Timestamp]
please check for overflow here:
```
def next(old: Timestamp) = if (old.millisSinceEpoch != Long.MaxValue) Some(old.next) else None
```
and similarly below. The whole point of the Option here is to be precise.