Debian packaging improvements

Some small changes to make the Riemann deb nicer to work with.
I think so. [Here's the section I found in the Debian policy manual:](https://www.debian.org/doc/debian-policy/ch-opersys.html#s-writing-init)

> The /etc/init.d scripts must be treated as configuration files, either (if they are present in the package, that is, in the .deb file) by marking them as conffiles, or, (if they do not exist in the .deb) by managing them correctly in the maintainer scripts (see Configuration files, Section 10.7). This is important since we want to give the local system administrator the chance to adapt the scripts to the local system, e.g., to disable a service without de-installing the package, or to specify some special command line options when starting a service, while making sure their changes aren't lost during the next package upgrade.