Subtape + Fix Recursion

[markus7800]

Hello,

I am not too familiar with the code base, but I updated the subtaping functionality to work for my own project. Maybe you find these fixes useful.

• Added subtapes property to TapedFunction This is important for task copying to work. We also have to copy the subtapes to continue in the correct instruction in the copied task (e.g. if we want to continue in a subtape).
• Remove translation optimisation based on constant return types of calls. A call may contain a produce statement but returns a constant. In the old implementation this call would have been optimised.
• Added a few test cases for subtapes that did not pass in the old implementation, but now do.

Best, Markus