Test and support Kubuntu 18.04/20.04

[jonchun]

Should support both Kubuntu/KDE Neon to give users a bit more of a choice. Preliminary testing seems good.

Found problems so far in Kubuntu 20.04

• libx11-xcb-dev and ibxcb-randr0-dev need to be installed additionally when building the Window AppMenu plasmoid.
• bottom default panel does not disappear (most likely the default panel in Kubuntu is not the same as the default panel in KDE Neon. I'm doing a check of widgets in the panel and if they are equal to the ones in default, it removes the panel. this was done to prevent the script from removing any customized panels)
• kwrite software not installed by default, but is a default pinned item. need to resolve this.

[jonchun]

Windows App Menu seems to not work for firefox only. Works fine in Dolphin, VLC, etc.

Firefox 74.0 (64-bit)

[Steinhagen]

You would need the firefox opensuse patch to have it working. By default, I don't think Kubuntu builds firefox with those patches, so I guess it's normal. On Arch Linux there is a separate community package for that: https://aur.archlinux.org/packages/firefox-kde-opensuse/

[jonchun]

Thank you @Steinhagen ! I'll look into that later.

[jonchun]

I couldn't get latte-dock to build on Kubuntu 18.04. Bug filed here. Hopefully it is just me being dumb. If it turns out that it is incompatible with the latest latte-dock due to wayland library incompatibilities I will be very sad :(

[jonchun]

In Kubuntu 20.04, when using the notification widget inside Latte Dock, I'm getting "Notification service not available". Placing it in a normal panel or the desktop, I properly see notifications.

This works fine in KDE Neon 18.04, so I suspect it has something to do with the versions of the libraries installed. Might file a bug report on this later if I can't figure it out.