Adds code in RasterizerStorageDummy to store off mesh surface information,
rather than just throwing it away. Without this, all surface arrays were
just defaulting to empty when the packed scene was written.
Added a dummy importer for textures to use with the server platform.
Allows for running a project in headless mode without crashing when loading scenes containing textured objects
Also as a result decreases load time as no image files have to be loaded.
