Bug fix for multiple channels

[maresb]

Line 115 of client.py should read:

self.clients[clId] = tuple([[] for _ in range(nSampl)]) # tuple of empty lists

Using [[]]*nSampl creates several references to just a single list. As a result, data from all channels is appended to each channel. This works for a single-channel device, but makes garbage for any device with more than one channel.