Filter by logging level of logger first and then by transport

[xaka]

It's very common to filter messages by logger's logging level first before filtering by transport's logging level. The reason behind it is that there should be an easy way to disable debug level (as an example)) entirely w/o updating configuration for each transport.

[indexzero]

The level ordering regression will get fixed in [email protected] via #290 or #349. The Transport level should always take precedence over the Logger level. The Logger level is only a sane default to use when the Transport level is not set.

That being said, all Transports should not default to any level.