Clean up graphite exporter definition

[colearendt]

Connected to #46

We fixed a small bug in host name detection (excluding dashes). However, we should harden this a bit:

• Make sure that Connect has the same flexibility to customize mappingYaml with values
• (probably unnecessary) pull into a library helper
• Figure out what characters are actually allowed in docker / kubernetes / helm as hostnames, so we can be sure that our regex captures all of them

It's also possible that the product will beat us to actually expose prometheus metrics and save us some work 😄