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 https://github.com/opencve/opencve/pull/139

Thank Lionel

[ncrocfer]

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

[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.