Adapt donations to use single location field #246

see #246 
Can you try to match `setDonorPanel()` to the old `setCollectionCenter()` and `setCollectionSite()` methods, in the sense that they take a `Long` as input parameter, not a `Location`, and the different method to assign this to the collectionBatch - e.g.:

```
public void setCollectionCenter(Long center) {
     Location l = new Location();
     l.setId(center);
     collectionBatch.setCollectionCenter(l);
}
```