enhance monasca agent process plug-in to return pid and command line string

The current implementation of process plug-in only returns the Process ID count of given process name, although it has a boolean named 'exact_match' which when set to true tries to find a process with exact name and if when set to false tries to search the name in command line string of all running processes.

For implementing monitoring of CEPH processes the above implementation is not sufficient as in case of CEPH there will be multiple processes/daemons running and we need to distinguish between these multiple processes using their respective command line parameters. This blue print is to enhance monasca agent's process plug-in to return the PID and command line string of all matching CEPH processes as part of VALUE_META attribute so that consumer can use this information to distinguish between different processes.

Although this enhancement is required for CEPH process monitoring but it is helpful for any other scenario where there will be multiple processes with spawned using command. This blueprint also adds a new boolean flag named 'fetch_details' in process.yaml file to control if the process plug-in need to return additional information or not.