[MonologBridge] Ignore empty context/extra by default in the ConsoleFormatter

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | 
| License       | MIT
| Doc PR        | 

This adds support for https://github.com/Seldaek/monolog/pull/388 and turns it on by default since the console output is arguably meant for humans and not for machine readable stuff it makes sense I believe. /cc @Tobion

**Note:** This depends on an unreleased version of monolog and should not be merged until 1.11 is out.