3D Beetle wrong initialization when project reopened, #MINOR #3566

3D Beetle does not initialize properly.
Steps to reproduce

1. Fresh Snap instance
2. Load the 3D Beetle Geometry library
3. Open a project containing 3DB blocks, say a (beetle view)
4. Library blocks does not work
5. Until you press the [Open 3D Window]

The library is auto-initialized at project load by the libraries/beetle/init.js
But the true initialization is inlined into beetle.js as an IIFE.

// Initialize the extension
(function() {

beetle.js is cached and loaded only once.
Initialization should be explicitly called at every init.js load.

Or loading a new project should reset extensions state.
Reported by the user on the forum