first creation of PID controller + adjustments to pumpingstation

src/pid/index.js

@@ -0,0 +1,11 @@
+const PIDController = require('./PIDController');
+
+/**
+ * Convenience factory for one-line instantiation.
+ */
+const createPidController = (options) => new PIDController(options);
+
+module.exports = {
+  PIDController,
+  createPidController
+};