Add configuration to start external compactions and scan servers

[DomGarguilo]

Right now when using uno if I want to start external compactions or scan servers I need to stop accumulo change the cluster.yaml within the install folder and then start accumulo back up. It would be nice to be able to have uno start these services for me.

[ctubbsii]

My workaround for special cases, when I want to diverge from Uno's default behavior, is to create a new branch in my fork that diverges from the main branch just slightly and makes the changes I want. I have found that to be more useful than adding a ton of options to Uno's config files and modifying its scripts to support those options.

In the case you're describing, I would probably just comment out the line in bin/impl/install/accumulo.sh that does accumulo-cluster create-config and place my own preferred cluster.yaml in conf/accumulo/common/. If one were to patch Uno to support this natively, rather than add more Uno config for the number of scan servers or external compactor services, I'd just make it do [[ -f conf/cluster.yaml ]] || accumulo-cluster create-config. That way, it doesn't try to generate a new config if you already have one copied in from conf/accumulo/common/, and then you just supply your own there.