Trim down interface

[yoshuawuyts]

I've been using femme for a while now, and initializing it always requires copying over some boilerplate. I wish we could streamline this slightly:

femme::info()?; // start femme with info log level
femme::trace()?; // start femme with trace level

In addition to that, something that env-logger does well is provide a way to filter messages. In reality these methods should be be a constructor for a Logger struct that can be further configured.

This would also allow us to trim down the submodules we have. When piping we should always print out ndjson. When printing to stdout we should use the pretty printer.

The "simple" printer becomes a bit of a strange one, but perhaps we don't need it per-se? I'm unsure really. Thoughts would be welcome here. Thanks!

[Fishrock123]

This issue seems like it was addressed in aa1fd83