Stopping macros

When a macro is stopped the function on_stop of this macro is called. A general function can be defined to be called when any macro is stopped.

When you program a macro, be aware:

if you use a call to:
```
  time.sleep()
```
Ctrl-C will only stop the macro after the time.sleep() has finished.
the macro will not be stopped at any point, but in some specific calls like:
```
  self.output()
  self.runMacro()
  self.checkPoint()
```
Introduce calls to self.checkPoint() in your code if you want to be sure to stop the macro at a certain point.

As a typ, instead of programming:

time.sleep(10)

it is more convenient:

self.checkPoint()
time.sleep(1)