Configuration: implement application name, version and client id

[dkropachev]

Make driver report application name, version and client id to server on startup message.

Fixes: #553

Tested:

cqlsh> SELECT client_options FROM system_views.clients;

 client_options
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                          {'CQL_VERSION': '3.4.7', 'DRIVER_NAME': 'DataStax Python Driver', 'DRIVER_VERSION': '3.29.0'}
                                                                                                          {'CQL_VERSION': '3.4.7', 'DRIVER_NAME': 'DataStax Python Driver', 'DRIVER_VERSION': '3.29.0'}
 {'APPLICATION_NAME': 'app_name', 'APPLICATION_VERSION': 'app_version', 'CLIENT_ID': 'client_id', 'CQL_VERSION': '3.0.0', 'DRIVER_NAME': 'ScyllaDB Java Driver', 'DRIVER_VERSION': '3.11.5.8-SNAPSHOT'}
 {'APPLICATION_NAME': 'app_name', 'APPLICATION_VERSION': 'app_version', 'CLIENT_ID': 'client_id', 'CQL_VERSION': '3.0.0', 'DRIVER_NAME': 'ScyllaDB Java Driver', 'DRIVER_VERSION': '3.11.5.8-SNAPSHOT'}

[Bouncheck]

Two points:
If the CLIENT_ID is not explicitly set, it should be randomly generated, right?

How can user later cross check the CLIENT_ID with the information he obtains from the tables? Should it be logged somewhere once at the start of the session?

[dkropachev]

Two points: If the CLIENT_ID is not explicitly set, it should be randomly generated, right?

No, user get to generate it on they own.

How can user later cross check the CLIENT_ID with the information he obtains from the tables? Should it be logged somewhere once at the start of the session?

It is their job, depends on deployment, on what they want, they may not use it at all.

[Bouncheck]

If it's meant to be set by the user only then I think it looks ok.

Having it randomly generated if unset could preempt some back and forth in case of user issues, but not having it on by default also saves some bytes.