Number of samples used for creating an arbitrary waveform
is now automatically adjusted.

- introduced a flag to indicate a continuous test
- increased the cooldown time
- more verbose output

- different test data sets depending on the pulse duration switch
- updated to the new PyBECO version
- replaced some functions with PyBECO library calls
- shows the pulsegen command for each test
- cool down period between tests

Updated gateware and hardware submodules to latest version and changed hardware submodule URL to write-mode