change verbosity behavior

[mattsb42-aws]

The verbosity flag controls how the logger is configured.

Current verbosity behavior is:

• nothing : no logging
• -v : WARN (global)
• -vv : INFO (global)
• -vvv : DEBUG (global)

After going through various scenarios and using the logging output, I decided a more useful approach would be:

• nothing : WARNING (aws_encryption_sdk_cli), CRITICAL (root)
• -v : INFO (aws_encryption_sdk_cli), CRITICAL (root)
• -vv : DEBUG (aws_encryption_sdk_cli), CRITICAL (root)
• -vvv : DEBUG (aws_encryption_sdk_cli), INFO (root)
• -vvvv : DEBUG (aws_encryption_sdk_cli), DEBUG (root)

WARN is always on for safety reasons: we want users to always be aware of WARN events.

[mattsb42-aws]

Addressed in https://github.com/mattsb42-aws/aws-encryption-sdk-cli/commit/15dc51a3184bb28add4690ef0404508f97d974c5

[juneb]

In this scenario, -v seems to have no effect. It's the same as omitting the parameter. I don't think that's a useful customer experience. If I'm using the default, but not getting enough info, I start by using -v and nothing changes. I recommend that the default (nothing), be errors only.

[mattsb42-aws]

Whoops, I mis-spoke in the issue details. Updated to reflect what the code actually does.