Adds health sensor assembly

Adds health sensor assembly to autolathe and some vending machines. Using this assembly is simple:
1. Attach.
2. Turn on.
3. Go suicidebombing!
You can insert it into grenade with healing smoke too.

In "detect crit" mode it will signal at 0hp, in "detect death" at -90hp.

This was tested on ss13.ru Green and White servers for ~6 months.
Why is this here? (In this file, instead of code/__HELPERS)