traccar: Traccar phoning home by default is not documented

It appears that Traccar phones home by default with the setting in default.xml.

<entry key='server.statistics'>https://www.traccar.org/analytics/</entry>

This is not documented for the configuration file; there is just a short mention in a forum post.

It appears the full server statistics is uploaded to the specified URL every day.

I feel that this should definitely not be enabled by default.