GitLab

- This allows to use additional features in the plugin, e.g. templates
for single sensors

- The interval field now defaults to the value inherited from the
sensor groups that the sensor belongs to
- Metadata blocks in templates can now be overwritten completely or
only in part

setting publish to false for sensors which get aggregated to another sensor (they shouldn't be published).

- Default C++ to_string implementation only supplies 6 decimal digits of
accuracy, truncating very small scaling factors
- Now using string streams

Implementing more cache info to avoid doing excesive job updates. Implementing all ratio metrics. Renaming some metrics which were missleading

Fixing issue with connection details and template for the persystsql operator. Updating examples of config files.

PerSystDB: adding job cache to avoid querying mysql job ids. executeOnStart and executeOnStop are now used in the PerSystSqlOperator.

In case sql connection is gone (error 2006), we finalize the connection to avoid memory leaks in mariadb lib.