Add co2_processing node implementation for pandora_software_tasks pkg

The co2 processor simply checks the value of incoming
co2 readings and if the value is above a set const
threshold, an alert is raised.

Changes to be made:
1) Adding a more sophisticated solution to the problem
   of human detection through co2 measurements
2) Adding unit and functional tests for the
   co2_processing node

	modified:   ../pandora_sensor_processing/CMakeLists.txt
	new file:   ../pandora_sensor_processing/config/sensor_processing/co2_processor_params.yaml
	new file:   ../pandora_sensor_processing/config/sensor_processing/co2_processor_topic_names.yaml
	modified:   ../pandora_sensor_processing/include/sensor_processing/co2_processor.h
	modified:   ../pandora_sensor_processing/launch/co2_processor.launch
	modified:   ../pandora_sensor_processing/src/co2_node.cpp
	modified:   ../pandora_sensor_processing/src/co2_processor.cpp
Modify co2_processor
Modify co2_processor parameters
Add co2_processor tests