Anet A8 BLTouch Holder

I tried the version made by jeanmichel, but it didn't work for me:
- original BLTouch version Smart is bigger
- when change hole for sensor then still had issue with distance from nozzle.
- original model had a couple of issues so Cura slicer didn't slice it correctly

So I decided to make a remix with a little bit changed dimensions and it fits perfectly for my Anet A8 now.

Changed blocks in Configuration.h for Marlin 1.1.6

Enable BLTouch
```
#define BLTOUCH
#define SERVO0_PIN 27