WPS process to rank points along a track/route

Update of ktcorby's efforts on PR#73
For readability?

```scala
val placeTimes = 
  boxFeatures.collect {
     case sf if sf.dateTime.isDefined => new CoordWithDateTime(sf.centroidCoordinate, sf.dateTime.get)
  }
val sortedPlaceTimes = placeTimes.toList.sortBy(_.dt.getMillis)
```