Overhaul of the StreamViewer

[mscheltienne]

The StreamViewer API needs an overhaul. It will be rename as Viewer to match the new Stream and Player API. The new Viewer API will interface with one or more Stream and will use methods from Stream to edit the stream properties:

• [ ] Possibility to change the channel names
• [ ] Possibility to change the channel types (will automatically adapt the trace colors, the trace y-range)
• [ ] Possibility to change the channel units (will automatically adapt the trace y-range)
• [ ] Possibility to set a filter per channel
• [ ] Possibility to set the EEG reference

Moreover, the Viewer should be able to connect to multiple streams. Streams with a regular sampling rate should be displayed as channels (/!\ identical channel names between streams must be covered) while streams with an irregular sampling rate should be displayed as vertical lines.

For the filter, some thinking is required to compensate or ignore the causal delay introduced on one or all channels (and between a regular sampling rate stream and the vertical lines from an irregular one).

The backend should be pyqtgraph with OpenGL for better display.

[mscheltienne]

For real-time annotation, the causality of the filter prevents us from getting a clear relationship between a location on the viewing area and a location in the saved dataset. PR #47 can serve as a basis for a second attempt.

[mscheltienne]

Depends on the overhaul of the Receiver API:

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