New field log.verbosity

There is a field log.level to capture the log level of the specific event but sometimes we need to know what is the application verbosity setting. I propose to add:
- log.verbosity

Use case 1: app setting verbosity is: DEBUG, there will be log events with log.level:ERROR to log.level:DEBUG.

Use case 2 (our use case): log.verbosity: header - system is logging only a header information, log.verbosity: payload - system is logging payload information