Remove unused/superseded signal format code.
Use latest generated Python code for BioSignalML ontology.
Remove 'index' property of an Event.
An EDFSignal does have an 'index' attribute.
Default to using 'szip' compression in HDF5 datasets.
'bsml:format' is no longer a property in the ontology.
Use keywords to name parameters to PropertyMap.
Use 'super()' when getting WebSocket handshake headers.
Defualt to using SINC_MEDIUM_QUALITY (instead of SINC_FASTEST) for libsamplerate conversions.