Test files needed for Rigol DS6000 scopes

[scottprahl]

The code is in the repository, but it is untested. A few sets of saved waveforms created by a Rigol DS6062, DS6064, DS6102, or DS6104 scope would fix this. Each set should contain

• file.wfm
• file.csv
• file.txt (created when saving CSV files with "Para Save" ON)

Ideally the saved waveforms would cover a range of vertical and horizontal settings.