UKC Forum Tweaks per Luke Horne

Very simple extension to make small changes on UKC Forum threads. The extension can:
- Hide likes and/or dislikes
- Hide posts from selected users
Options for both these actions can be configured in the extension's options. The default behaviour is to blocks likes and dislikes but not to block posts from any users.

All the code (what little there is of it) can be viewed on GitHub: https://github.com/Luke9090/UKCext/