FR: when running locally, it would be nice if there is a way to pass custom credentials and project ID to dev appserver

There is apparently a way to pass app-id when you start up the GAE Java runtime locally. At the very least, it would be good (helpful to Veneer) if:

~~`com.google.appengine.application.id` System.property() were set.~~ UPDATED by @chanseokoh: this property won't work.