2.9.0

Major changes

• Deprecated Device.model_number, Device.model_name, Device.manufacturer. Use
  Device.model link and new DeviceModel neurodata type instead. The old Device.model_name
  corresponds to the new DeviceModel.name. (#608)
• Added DeviceModel neurodata type to represent the model of a device instead of a specific instance of a device.
  This deduplicates information when a session involves multiple instances of the same device model, and it helps
  combine data across sessions and experiments when the model is the same.
  See #607 for details. (#608)
• Added BaseImage and ExternalImage as new neurodata types. The first so both Image and ExternalImage
  can inherit from it. The second to store external images (#604, #623, #627)
• Changed NWBFile.electrodes from a generic DynamicTable with added columns to a new ElectrodesTable
  neurodata type that extends DynamicTable with added columns. (#539, #624)
• Changed DecompositionSeries.bands from a generic DynamicTable with added columns to a new FrequencyBandsTable
  neurodata type that extends DynamicTable with added columns. (#610)
• Made SpikeEventSeries.timestamps explicitly required as described in the documentation. (#629)
• Allowed EventDetection to have shape (num_events, 2) to store the channel index of the detected event. (#620)

Minor changes

• Made group quantities consistent ("1 or more") across data interfaces / wrapper types (#613)
• Fixed typo and removed HTML tag from doc of behavioral neurodata types. (#600)
• Improved the documentation of IndexSeries. (#614)
• Made EventDetection.times optional and deprecated. Use source_idx instead. (#620)
• Clarified documentation of PlaneSegmentation that at least one of image_mask, pixel_mask,
  and voxel_mask is required. (#636)