Append --env option to all console commands

All Symfony console commands come with a --env option to control the Symfony environment they will run as. Currently, this option needs to be manually added to the :symfony_console_flags variable in order to work properly.

This pull request appends the --env option to all console commands by default. I have added the functionality to the existing set_symfony_env task, since they share the same purpose.

Please let me know if you would like me to update anything or would rather go about this differently. Thanks!