[HttpKernel][MonologBridge] PSR-3 support

This enables PSR-3 support and monolog 1.3+. The first commit is the main part. The rest deals with deprecation of short-hand methods (warn/err/crit/emerg) that are fully expanded in PSR-3 (warning/error/critical/emergency).

The downside of deprecating them is that for bundles it's a bit harder to support older and newer versions. If that is too much of a hassle you can drop that for now and cherry pick the first commit.

The upside is that it forces people to move towards PSR-3 compatible stuff, which means eventually we could completely drop the LoggerInterface from the framework. In any case I think the documentation should only mention the `Psr\Log\LoggerInterface` and people should start hinting against that. The change should be done in core as well I suppose.

Anyway I wanted to throw this out there as it is to get feedback.