Experiment with Kea exporter

We found there's existing Kea exporter here: https://github.com/mweinelt/kea-exporter

The goal of this task is to try to set it up and evaluate its usefulness.

Take the following aspects into consideration:

• it was written for kea 1.3. Does it work with 1.6? There were very few changes, except @Franek12 change that lets kea keep more than one data point for every statistics (it was always 1 for 1.5 and before, it's by default 20 for 1.6-beta1 and later)
• how tricky it is to expand it to report multiple data points (20 or however many kea reports) for each statistic
• what's the license (can we use it)
• how easy it is extend it in general (is it good source base?)

Keep in mind that the goal for now is to make it functional, but in the future we want it to be performant. If the data handling process is not efficient, make notes and possibly propose improvement (but don't write any code yet).