Adjusted Frontcase and Lens Adapter for VR Headset for OnePlus One

These are some fixes for thing 686737 (VR Headset for OnePlus One):
- I shrinked the lens threads so they fit without much sanding
- I shortened frontcase_new in order to improve the focus and the FOV
- I shortened the lens threads which reduces screen occlusion and thus increases the FOV

Have fun!