IVE: FunctionType editing
When the type has context parameters,it should be possible to set a different value at each instance. At the moment it's not possible:
the context parameters Name and Type cannot be modified, and it shall not be possible to Add/Remove context parameters in instances. However the Value shall be modifiable.
there should be no "Implementations" tab for instances, since it's not possible to modify the implementation of an instance. It's set by the type.