Initial plugin runtime api implementation

test/resources/plugin/test-plugin/test-runtime-plugin.js

@@ -0,0 +1,10 @@
+module.exports = function(RED) {
+    console.log("Loaded test-plugin/test-runtime-plugin")
+
+    RED.plugins.registerPlugin("my-test-runtime-only-plugin", {
+        type: "bar",
+        onadd: function() {
+            console.log("my-test-runtime-only-plugin.onadd called")
+        }
+    })
+}