Port examples from qcstm

[jmid]

STM's predecessor https://github.com/jmid/qcstm contains a range of examples https://github.com/jmid/qcstm/tree/master/examples

We should port these to STM which would allow to run them both sequentially and in parallel mode.

The primary difference is that qcstm's run_cmd : cmd -> state -> sut -> bool has two tasks which is broken in two in STM:

  val run : cmd -> sut -> res                 (* for interpreting the command over the system under test *)
  val postcond : cmd -> state -> res -> bool  (* for checking the post condition *)