Fixed Issues since Linux Mint 19 BETA

All editions
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artwork:
  - mint-x:
    - no icons in Online accounts > Information about Gnome online accounts -> Gnome Contacts, Gnome Documents, Gnome Maps and Gnome Photos
  - mint-y:
    - thunderbird icon isn't the same as its flatpak
    - in nemo additional pane, select a folder in the left page, click in the right pane. The selected folder in the left pane is white on grey, almost invisible.
    - video and subtitle icons are too similar

- The fortune command says 'no fortunes found' -> leftover, fortune is now removed.
- gdebi doesn't install packages unless it's run from the terminal

Cinnamon Edition
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- goa: ubuntu SSO isn't functional -> it won't work without snapd, and it's useless for anything else. Ubuntu non-gnome users auth in snapd CLI anyway, so this should be removed. We don't need it, it's not necessary and it won't work OOTB.

MATE Edition
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Xfce Edition
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