Split build and install into different targets: deps and depsinstall for dependencies, all and install for DCDB components

* 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.

Found some memory leaks in DCDBLib and fixed
a bug related to thread handling in CollectAgent.

Use the -r option to get raw values instead.