Remove config groups

Refactor away the config group concept and simplyfy the way config
fields are defined.  Fields are defined directly as properties of the
static field fieldDefinitions on the class itself with a separate
interface to declare the types of fields.

This makes it possible to easily make accessing the config fields type
checked in a way that lets plugins extend the interfaces with their own
config options by adding additional fields to the interface via
declation merging.

test/controller/InstanceInfo.js

@@ -17,9 +17,6 @@ describe("controller/InstanceInfo", function() {
 				assert.deepEqual(InstanceInfo.fromJSON(json, "controller"), info);
 			}
 
-			if (!lib.InstanceConfig._finalized) {
-				lib.InstanceConfig.finalize();
-			}
 			const config = new lib.InstanceConfig("controller").toJSON();
 
 			check(InstanceInfo.fromJSON({ config, status: "stopped" }, "controller"));