Support Classes : Part 2 Code generation

[ghaith]

Is your feature request related to a problem? Please describe.
With class parsing now in place, we need to support instances and method calls for such classes.

Describe the solution you'd like

• Classes should be treated as POUs and instantiated in a similar way to function blocks (This should happen automatically, but we need to add tests for it)
• Methods should be called in a similar way to Actions, with the exception that they need to always be fully qualified, either with an instance name or with a THIS keyword (Not yet implemented).
• In addition to the normal parameters, methods should also get their own POU as the second parameter. This can be done in a similar way to functions. And can be solved generically for all implementation (i.e. if an implementation has a container, the first param is the container, and if available, the second param is the pou with the name of that method)
• Tests for method calls are missing, but method calls without parameters should already work as actions (It will find the method even without the THIS pointer, which we should however fix or discuss this further while implementing)

We should not consider polymorphism and access rules at this stage

[ghaith]

#253 covers most of this story.
We would still be missing the THIS pointer.