Add setters and support for methods which return various types

The problem

Right now, we don't support setters on derived types. In addition, we haven't checked that we support having different kind of return types from methods.

Definition of "done"

• float
  • setter
  • support for method that returns this type
• int
  • setter
  • support for method that returns this type
• boolean
  • setter
  • support for method that returns this type
• array
  • setter
  • support for method that returns this type
• character
  • setter
  • support for method that returns this type
• derived type
  • setter
  • support for method that returns this type

Additional context

This is required to be able to properly test !74 (closed)