Major refactor and bugfix

[mesudip]

Fixes

• Larger request body #9 default client_max_body_size for all servers can be set with environment variable CLIENT_MAX_BODY_SIZEin nginx-proxy.
• Renewing of SSL certificate failed #11 Fixed issue with SSL auto renewal.Now container log also prints the SSL expiry details.
• SIGTERM is handled properly so that the container stops itself on docker stop command.

Features

• Basic authorization support
• Support for redirection domains.
• Nginx directives like client_max_body_size can be directly added to VIRTUAL_HOST

Code Refactor

• Separated code responsible for each feature like, vhost, ssl, basic auth, redirection as separate file in modules nginx_proxy/pre_processors and nginx_proxy/post_processors