Draft JEPs for primitive class features

[Suminda Sirinath Salpitikorala Dharmasena]

Perhaps another marker to add is Signed <: IntegerType with a view to add
unsigned later.

With possibility of enhanced arrays like <MyClass & MyInterface>[] x or
MyClass & MyInterface x[].

This way arrays need not have own markers. But still reference and value
arrays are desirable to control layout of data.