Fix print statements and deprecated time.clock

[MichielsenM]

time.clock doesn't exist in Python 3.8, so I think process_time() (or otherwise perf_counter() ) would be a suitable replacement.

[rieder]

Thanks Mathias
I'm not sure if we should merge these or not - the fixes are good, but I think these files might better be removed altogether.
The examples in examples/applications have I think all been replaced by newer versions in examples/textbook.
The test_sync.py file in the ph4 dir likewise seems a remnant of early developing.
@ipelupessy what do you think?

[ipelupessy]

I think we should retain them, textbook is text book and seperate; I think the ph4 development thingy may still be used by @stevemcmillan at some point

[ipelupessy]

@rieder merge?

[rieder]

merged