RFC: Taskotron task description format

[Kamil Paral]

> Another question is whether this yaml based task description is worth
> doing or if we should just use a python-based task format similar to
> what autotest does (inherit from a python class and override methods as
> needed).

I find this yaml format much more readable and simple. It's definitely more restricted than what you can do in a full programming language. But unless we really need the full programming power, I'd rather stay on KISS side.