Mark more strings for translate

I hope there isn't more string need
to mark for translate.
Update POTFILES.ui
Add domain="gnome-tweak-tool" into shell.ui for gettext

This allowing to translate the content of the app menu.
Tweaks title should be bold
Move background options to desktop group
Move scaling factor to legacy group
Move window options to window group
Move workspaces on primary to workspaces section
Add mouse tweaks (and middle click paste) to new group
Generalise a getter/setter tweak
Remove dead code
Move lid-close-suspend to power group
Move location entry tweak to desktop group
Remove default-monitors-setup
Fix typing options packing
Move legacy to xkb and update POTFILES
Rewrite autostartmanager to support GAppInfo
Only support nautilus when started by gsettings
Give tweaks a reference to the main window
Refactor tweakgroup datamodel to allow later loading