[FEATURE] Automatically stop the dev server when the clean task is run

[Insprill]

Occasionally I'll end up running Gradle's clean task while the dev server is running, causing the task to fail, and the dev server to break as some of its files have been deleted. Ideally, when the clean task is run, the dev server would be terminated.

I initially tried to implement this myself, however, it doesn't look like there's any good way to terminate a JavaExec task and I didn't want to get too deep in the weeds of alternate solutions.