Add an option to start zinc in the foreground

[erikswanson]

There is currently no option to prevent zinc -start from putting Nailgun in the background. This is a problem if I want to use something like runit to keep zinc running (after reboots or zinc crashes, etc).

An ideal solution would include this option making the zinc script use exec to start the JVM, so that signals work correctly.

(This would be a pull request, but getting $work to sign off on the CLA would take ages, sorry.)

[gkossakowski]

Hi @erikswanson! zinc is a maintenance mode at the moment so submitting PR is still your best bet to get this done.