Starting work to make Cake PSR-3 compliant and accept monolog as an
alternate logger without much pain
Using log instead of write in log engines and updating tests
Updating tests
Moving log formatting out of LogTrait.

This feature becomes limiting very easily, specially when having custom
loggers trying to format the message differently.
Fixing and adding tests for formatting complex data in loggers
Log::write() now accepts a scope key in last argument.

If a numerically indexed array is passed, it will understood as the
scope key.
Chaging the $scope parameter name to $context
Deprecating LogIterface, it will be removed before the stable version
Merge pull request #4675 from cakephp/3.0-psr-3

3.0 - Adding PSR-3 support