vim700: spelllang=en spell

- Data access
    - (*) Data access via network
    - Data caching
    - Create update_jobs() method.
    - Create update_channels() method.
    - Display non-existing channels in model
    - Sort channels in model
    - Display channels as tree

- Measuring
    - Markers
    - Store extrema and average values in list.

- Context menu
    - Find extrema
    - Last hour
    - Use value for all layers.

- Export
    - PNG
    - (*) CSV
    - (*) Delta-t specification

- Persistence
    - Sections
        - Markers
    - Preview

- Widget
    - Display combined gaps below time scale
    - Mark gap borders with lines.
    - Section properties with double click.
    - Avoid crash on zooming out infinitely.
    - Draw headers in pixmaps.
    - Draw section data in pixmap.

- GUI
    - Load file via command-line
    - Print resolution
    - Proceed, if channel is not found
