Add Nginx to the webapp container

[puntonim]

Follow up with what discussed here: https://github.com/nimiq/ansible-biostar/issues/8#issuecomment-46962907

First make sure waitress really cannot write a proper access log and if so introduce Nginx to:

• serve static files
• serve pyhton code via waitress
• log
• protect against this: https://github.com/INCF/biostar-central/issues/40#issuecomment-46780167

[puntonim]

Done f43098ea309c12dfbacc5903a07d1c18df41c2c5