Add support for PPG, ACC, and GYRO streams to viewer

[jdpigeon]

Following the recent 2.0.0 update, we still need to update the viewer in order to be able to plot data from the alternate data sources.

This should be fairly straightforward, with some work already done in Hubert and Stephen's PRs

[kylemath]

hey guys, good work on this, I got a viewer working with PPG as a hack yesterday, changed line 81 of viewer_v2.py

    streams = resolve_byprop('type', 'EEG', timeout=LSL_SCAN_TIMEOUT)

    streams = resolve_byprop('type', 'PPG', timeout=LSL_SCAN_TIMEOUT)

also need to adjust the filter on ln 116:

        self.bf = create_filter(self.data_f.T, self.sfreq, .5, 15.,