GitLab

- Allows to reduce the size of the query results considerably

- overloaded query() and fuzzyQuery() methods that allow to query a set
of sensor IDs at the same time
- also changed the behavior of fuzzuQuery(): only one query is performed
now, retrieving the most recent value BEFORE the specified timestamp

- If users specify a single timestamp (startTs==endTs) when performing
a sensor query through dcdbquery or libdcdb, a fuzzy sensor query is
performed, and the closest sensor reading to the target timestamp is
returned

- String topics are now used across all of DCDB, up to Cassandra
- As of now, sensor names ALWAYS match MQTT topics
- Users can still define sensor "aliases" via dcdbconfig that point
to the same topics

- Added configuration options to tune the Cassandra driver for
optimal performance
- Added a "debugLog" configuration switch that enables logging of
errors in asynchronous inserts in the Cassandra driver

Add SensorDataStore::insert function to insert SensorDataStoreReading objects instead of (sid, timestamp, value) tuples

use the new dcdbconfig db fuzzytrunc command to remove entire rows
of data that are getting too old.

Remove debug message from sensordatastore. Handle missing montblanc.conf in Slurm plugin more gracefully.

of the new super-simple C API in DCDBLib.

Make Mont-Blanc SlurmPlugin link against this C API.

* Extended DCDBConfig and SensorDataStore to provide functions for querying data
* Adapted dcdbquery accordingly
* Project now compiles again but dcdbquery likely to be broken

* Added SensorConfig and DCDBPublicSensor classes as interface for dcdbconfig
* Fixed bugs and tested:
  --> CollectAgent fully working
  --> dcdbconfig fully working

* Bump cpp-driver to 2.0.1
* Create new SensorId header/source that takes over the logic
  previously found in SensorDataStore related to populating
  SensorId structs from MQTT topic strings and serializing
  them into Byte Arrays to be used as Cassandra Row Keys.

* Bumped Cassandra to 2.1.5
* Bumped cpp-driver to 2.0
* Eliminated cassandraBackend in favor of DCDBConnection

In the future, a DCDBConnection handles the low-level connection
to Cassandra. On top of an established DCDBConnection, you can
create a SensorDataStore object which gives you access to raw
sensor readings.

Related to ticket #29.