Integrate sbt-native-packager

[davegurnell]

The end goal is to turn this into a .deb or .rpm so it can easily be installed on a server.

We want the app to be configured from /etc. We probably need a whole directory under /etc to contain both the conf file and any message templates.

[fommil]

it'd be great if the /etc/concierge/templates/ folder was structured to contain owner/repo files, so that there would be no need to provide this information in the config file (and also support multiple repos!)