Check that static class properties can be accessed for read and write and
that they are shared between all instances of a class type.
Check that this works for the following 3 cases
* accessing the static property in a class function or task
* accessing the static property in a class function or task using `this`
* accessing the static property on a class object instance
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>