TODO

1. 
change identifier from 123.0 to textgrid:123.0 in all/the getRecord requests,
must be equal to the identifiers we get with the getIdentifiers() method 
DONE

2.
implement sets (for the prootype :)
DONE

3.
implement resumption tokens (later)
DONE
4.
remove "yo" in class RecordDeliverer :-)
DONE

5.
DONE :D

6.
Fetch earliestTimestamp from ElasticSearch?
DONE