Big rework of registry.js

Part of #322

Loads node.html files before node.js files

Adds helper.unload which must be called by node tests
to clear the registery of nodes

test/nodes/core/storage/28-tail_spec.js

@@ -42,7 +42,7 @@ describe('TailNode', function() {
     });
     
     afterEach(function(done) {
-        
+        helper.unload();
         fs.exists(fileToTail, function(exists) {
             if(exists) {
                 fs.unlinkSync(fileToTail);