Chore: Move services into core

- Move app/, worker/, websocket_server/, migrations/, tests and the services to core/, which becomes a self-contained root
- .gitmodules path for the novnc submodule rewritten by git mv.
- Initial Step to split into core and cloud/community

.gitmodules

@@ -1,5 +1,5 @@
 [submodule "app/static/novnc"]
-	path = app/static/novnc
+	path = core/app/static/novnc
 	url = https://github.com/novnc/noVNC.git
 [submodule "sandbox/joke_container"]
     path = sandbox/joke_container