Symfony Dotenv Component Fixes

[aaronj-ep]

Allows the bundle to be used with environment variables in the specified configuration. Previously, runtime variables were not properly resolved in the propel.configuration and propel.build_properties services.

Additionally, normalization performed on configurations using environment variables failed, as at the time of normalization, the data was a placeholder, rather than the real configuration data.

With this pull request, the following was changed to allow for proper behavior:

• The dbal & build_properties sections of the configuration are saved as parameters.
• The propel.configuration, propel.build_properties and dependent services are now synthetic services.
• The synthetic services are injected into the container at runtime.

Additionally, some other minor deprecations were handled.