[Console] Added standalone PSR-3 compliant logger
feature #3696 [Console] Added standalone PSR-3 compliant logger (dunglas)

This PR was merged into the master branch.

Discussion
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[Console] Added standalone PSR-3 compliant logger

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs?     | yes symfony/symfony#10194
| Applies to    | 2.5

Commits
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15628e6 [Console] Added standalone PSR-3 compliant logger