The rasterisers (both GLES3 and GLES2) were calculating their own frame delta time
This fix lets the rasterizers get the frame delta through the draw call
That way any regulations to the frame step from the main script will not cause particle systems to process at a different step than the rest of the Engine.
Remove unused rasterizer storage variable
frame.prev_tick variable were not used anywhere and has been removed
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.
