Remove Dockerfile in favour of OpenFaaS Golang template - Part 1

The Dockerfile is now unnecessary - Derek was developed before the Golang templating system, so we should move the code to use the Golang template for less to maintain, more frequent watchdog updates and other fixes done in the Golang template.

```sh
faas-cli new --lang go derek
```

Since the Golang template uses the classic watchdog and allows for forking per request, no other changes are required to prevent os.Exit/panic handling.

The various environmental variables can be moved into there derek.yml file.

Once refactored part 2 can take place #96