Add a fifo to buffer collected data when the server is not available

This commit adds a `BoundMetricsFifo`, that has a certain capacity to store metrics. When it gets full, old ones are evicted.
The `RestForwardingHandler` makes use of this fifo to buffer data and only removes metrics from the fifo, when the http response code of the server is 200 or 204
Maybe  easier to read:
```bash
VERSION=`mvn help:evaluate -Dexpression=project.version | grep -vF "[INFO]"`
```
Is there a reason to keep old line commented out?