-add implementation for calieventdatastore
-requires adaption of CA, Pusher to actually store data in it

-CED should go into separate table
-adds header files for required libdcdb extension
-add other sideshow stuff required for new Cassandra table
-actual implementation outstanding

1. Check for nullptr if metadata is set. 2. Changing scaling_factor to be multiplied instead of divided (dcdb nomenclature).

-can send event data from cali service to pusher plugin
-refactored sample data symbol lookup: is now done by cali service
-cali service only sends timestamp and data-string to pusher plugin
-outstanding TODO: push event data into separate Cassandra table

Removing puning of ints to doubles and viceversa, and implementing use of scaling factor from metadata

- Especially useful in Collect Agent: now there is no need to restart
the CA to instantiate operator plugins after sensors have been
published

- Collectagent uses published TTL values and caches received metadata
- READMEs updated accordingly

- Also added a "pattern" field to SensorMetadata class for consistency
with the DCDB::PublicSensor class

- Complies with the rest of the interface in libdcdb

- Metadata is now parsed from config files, sent from Pushers to
Collectagents as JSON, and finally written to Cassandra

- JSON metadata is sent only if a "metadata" block for the sensor is
defined, else if auto-publish is enabled we only send the sensor name

- Now supports publishing of metadata information as well

- Also renamed "frequency" column to "interval", can be used for all sensors

- Added override qualifier to nextReadingTime() in IPMISensorGroup
- Re-added mariadb to list of dependencies

- Data is correctly parsed from DCDBPusher, sent as JSON, and received
by collectagents
- Integration in libdcdb is still pending

SMUCNGPerf Operator: implementing memory bandwidth. PerSystSql Operator: fixing issue with one unit not being present, and no calculation was done.

- Now is header-only to make SensorBase happy

- Implementation has been split into a SensorMetadata class and a
MetadataStore one to simplify integration in DCDBPusher and Collect Agent

Merge branch 'development' of https://gitlab.lrz.de/dcdb/dcdb into development