Adds primitive implementation for /cilent.computer_id

[Altoids1]

Fixes #181

Right now we're really just waiting for RobustToolbox to implement something rigorous.

For now, we're just MD5ing the ckey.

Note

In the future, I'd like to implement some sort of suite of security warnings to caution against using computer_id and other security-insecure things like this. Probably after the warning rework, whenever that happens.