toolbox: Improve io
toolbox: Improve test suite
toolbox: Add type Toolbox_Natural32
toolbox: Add type Toolbox_Natural16
math: Enable conversion to packed color models
joy: Improve joy
toolbox: improve reference counting semantics

The reference count of an object is not considered as part of its state anymore but rather as run-time information about
the object. Incrementing/decrementing the reference count of objects referred to by a const pointer is explictly allowed.
The documentation states this explicitly now. Furthermore, the ref and unref functions of types now all accept constant
pointers to objects of their type as their argument now.