Fix missing app ID and icon on Wayland.

[lightbulbjim]

X11/Wayland needs to know the name of the .desktop file to show a dock
icon and application name. X11 has various means of guessing the
filename (often WM_NAME). Wayland is a bit more strict, and requires
that either the filename match the AppId or the .desktop filename be
specified.

By specifying the .desktop filename QT will set the AppId automatically (from the Exec field I believe):

$ WAYLAND_DEBUG=1 ./result/bin/qtpass |& grep 'xdg_toplevel@[0-9]\+\.set_app_id'
[4110074.755]  -> xdg_toplevel@23.set_app_id("qtpass")

Tested on a Gnome 3.32 Wayland session. To run using XWayland, set QT_QPA_PLATFORM=xcb. To run using Wayland set QT_QPA_PLATFORM=wayland.

[coveralls]

Coverage decreased (-0.008%) to 7.001% when pulling aba8c41 on lightbulbjim:wayland-appid into 9a15ef3 on IJHack:master.

[codecov]

Codecov Report

Merging #468 into master will decrease coverage by <.01%.
The diff coverage is 0%.

@@            Coverage Diff            @@
##           master    #468      +/-   ##
=========================================
- Coverage    7.41%   7.41%   -0.01%     
=========================================
  Files          44      44              
  Lines        2765    2766       +1     
=========================================
  Hits          205     205              
- Misses       2560    2561       +1

Impacted Files	Coverage Δ
main/main.cpp	0% <0%> (ø)	⬆️

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