NGINX bot blocker

[aksm]

What?

Corresponding issue for esmero/archipelago-docker-images#61. As mentioned there, we'll need the following:

• environment variables for configuring, enabling/disabling cron, and enabling/disabling the includes for the bot blocker
• commented out lines in the docker-compose.yml for the image, the above variables, and the below folder
• one persistent folder for mounting to local config_storage/nginxconfig/bots.d, which will contain the continually updated block/permit lists
• an added include to the nginx.conf.template file to dynamically import another template file that will be modified (based on environment variable) when the docker ensemble is brought up.