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* Correlogram plot supports new square plot matrix mode and count per second
in addition to per segment.
* New options in spike waveform plot.
* DataProvider objects support transparent lazy loading for compatible IOs
(currently only Hdf5IO).
* DataProvider can be forced to use a certain IO instead of automatically
determining it by file extension.
* Load parameters for IOs can be specified in DataProvider.
* IO class, IO parameters and IO plugins are saved in selections and properly
used in startplugin.py
* Qt implementation of ProgressBar available in plot.helper (moved from
Spyke Viewer).
* Loading support for IO plugins (moved from Spyke Viewer).