Nullness Type System for key.core

[wadoon]

More nullness type system checks. Now for key.core.

I want first to merge #3399 into KeY to avoid double work.

[wadoon]

I have pushed further and activated Nullness checks for more packages but have not finished everything. Annoying are the situations where the InitilizationChecker hits:

class A {
  public A() { ... 
    setFoo(2);
  }
  void setFoo(int i){...}
}

The complain is that setFoo is called with @Unintialized A this but expects @Initialized A this.

@wmdietl @flo2702
Is there any trick to get pass this message? For example, an

assert this instanceof @Initialized A;

would be fine.

Inside KeY, we have many of these moments. It is also not a bad code design and is hard to avoid. Also adding the right annotation leads to ugly code:

class A {
  public A() { ...; setFoo(2);  }
  void setFoo(@Uninitialized A this, int i){...}
}

and this needs to be added to all transitive called methods.