about: add important contributors
timeline/elements: don't show all the keyframes when group selecting.

Optimization to workaround clutter being sluggish.
timeline/previewers: don't try to show waveforms when pixelWidth == 0.

Otherwise we divided by zero.
timeline: commit for each container ungrouping.
project: no need to set auto_transition after starting to extract timeline.
pipeline: when not in RENDER, the pipeline can and must recover

... from errors.
render dialog: Don't show keyframe button for codec properties.
waveforms: take in_point and duration into account.
elements: let the backend update keyframes correctly.
project: cast width and height when they are set through properties.
GstDynamicWidget: port combobox to Gtk3 API.