Packetry needs an icon

[mossmann]

We need an icon for the Windows executable and the Linux AppImage. We may also need it for macOS in the future.

We have had one icon design proposed (#95) so far.

As explained in this comment we'd like something that is less specifically USB-related, and we also hope that the icon can somehow represent a tree.

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One concept we've had internally is to represent the interleaved "packet tree" directly:

This alternative is meant to look like a tree and to abstractly represent Packetry's interleaved tree. Drawbacks we've noted are that it doesn't look great at small (16x16) size, that it has perhaps too many nodes, and that, other than a suggestion of interleaving, the spatial positions of the nodes do not have any meaning. Packetry is the only tool we know of that visualizes overlapping trees with a global ordering of nodes, so it would be nice if the icon were to represent that unique capability.

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This variation is meant to more accurately represent Packetry's data model. With time represented by the vertical axis, each node is at a distinct time. No two colors share a column (which I don't think is meaningful in the internal data model but is similar to how the graph is displayed to the user in the UI; there is only one event per row in the traffic pane). Parent nodes are below their children (A parent node in Packetry has the same time stamp as its first child, but it precedes its first child in the global ordering.) and share a column with one child. Drawbacks are that it looks less like a tree (the organic kind), more like a hand, and isn't great at small size (though this can be improved by spreading out the nodes).

[mossmann]

We plan to use this icon temporarily: https://github.com/GNOME/adwaita-icon-theme/blob/master/Adwaita/scalable/mimetypes/application-x-executable.svg