Reversed Pentax K-mount to Neewer macro ringlight adapter

Adapter to attach a _reversed_ Pentax K-mount lens to a Neewer macro led ring light.

Like the lens cap this is remixed from, the k-mount tolerances are fairly tight, so some manual cleanup may be required to allow this to install smoothly.

## Changelog

05-Jul-2018:
* Rebuilt k-mount and threads from scratch (and so removed the remix) to reduce friction, fix alignment.
* Added grippy notches to outer ring
* Added lens alignment dot
* Added recess and notches to allow 52mm snap-cap