Add randomInteger() to new GeneralHelper

Where a helper is hard coding a UUID for a field is going to be easy to make unique; we just call our `GeneralLib.generateUUID()` function.

But many helpers also need to generate references, licence number being a good example. If we are going to make these unique we're going to need a means to generate random numbers. Often they need to be within a certain range, for example, 100 to 999 because the number must be a certain number of digits long.

So, we're adding a new `randomInteger()` function which can handle this requirement. Doing so forced us to make a decision as to where to put it. We decided to create a `GeneralHelper` module that can be used going forward for any shared functionality in the helpers.

test/support/general.helper.js

@@ -0,0 +1,24 @@
+'use strict'
+
+/**
+ * General helper functions available to all helpers
+ * @module GeneralHelper
+ */
+
+/**
+ * Generate a random integer within a range (inclusive)
+ *
+ * @param {Number} min lowest number (integer) in the range (inclusive)
+ * @param {Number} max largest number (integer) in the range (inclusive)
+ *
+ * Credit https://stackoverflow.com/a/7228322
+ *
+ * @returns a number between min and max (inclusive)
+ */
+function randomInteger (min, max) {
+  return Math.floor(Math.random() * (max - min + 1) + min)
+}
+
+module.exports = {
+  randomInteger
+}