Add redirect log to stdout and config to new feature

[lprat]

I added option gnucorn to get output log to stdout.
And I added configuration for feature pushed on PR opencve/opencve#139

Thank
Lionel

[ncrocfer]

I let @ldurnez checks for the Gunicorn option, but please remove your custom configuration on opencve.cfg file because opencve/opencve#139 has been closed. The comments are in my detailed answer.

[ncrocfer]

To remove.

[ldurnez]

Hello,

Can you use variable inside the .env to configure these variable inside docker-compose file? As it has been done for the opencve_port variable for instance:
${OPENCVE_PORT:-8000}

This way, we keep compatibility and easy configuration for everyone that use different worker number etc.