Have a service variable for each container's mDNS

[MatthewCroughan]

Each service should have a configurable mDNS hostname. For example, if the fleet variable MDNS = 1 and GRAFANA_MDNS_NAME = grafana then the grafana container should broadcast on grafana.local.

[MatthewCroughan]

Relates to #11

[ajlennon]

ok

[MatthewCroughan]

I'm working on this here too MatthewCroughan/octobalena#3

So I'll implement it there first and then suggest changes here.