Documented info method
feature #4047 Documented info method (WouterJ)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #4047).

Discussion
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Documented info method

| Q   | A
| --- | ---
| Doc fix? | no
| New docs? | yes (symfony/symfony#11453)
| Applies to | 2.6+
| Fixed tickets | -

Commits
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37d5361 Documented info method