[ParamConverter] Improving documentation
merged branch gnugat/doc-converters (PR #205)

This PR was squashed before being merged into the master branch (closes #205).

Commits
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96944d1 [ParamConverter] Improving documentation

Discussion
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[ParamConverter] Improving documentation

This PR provides a `yml` configuration example for the service registration in the documentation, and some PHPdoc to the interface, the DoctrineParamConverter and the DataTimeParamConverter.