setting-dialog: Add keywords to .desktop files

Bug: 16621

Add keywords to the desktop definition files.

settings-dialogs/xfce-wm-settings.desktop.in

@@ -2,6 +2,7 @@
 Version=1.0
 _Name=Window Manager
 _Comment=Configure window behavior and shortcuts
+_Keywords=windows;management;settings;preferences;themes;styles;decorations;title bar;font;buttons;menu;minimize;maximize;shade;roll up;layout;keyboard shortcuts;focus;snapping;screen;workspaces;edges;corner;hide content;move;resize;moving;resizing;double click;
 Exec=xfwm4-settings
 Icon=xfwm4
 Terminal=false

settings-dialogs/xfce-wmtweaks-settings.desktop.in

@@ -2,6 +2,7 @@
 Version=1.0
 _Name=Window Manager Tweaks
 _Comment=Fine-tune window behaviour and effects
+_Keywords=windows;behavior;settings;preferences;cycling;cycle;switching;focus;raises;accessibility;key;dragging;move;moving;hide;frame;title bar;maximized;tile;screen;edge;hot corner;snapping;mouse wheel;roll up;workspaces;placement;compositor;compositing;enable;disable;shadows;decorations;opacity;resize;inactive;preview;compiz;transitions;
 Exec=xfwm4-tweaks-settings
 Icon=wmtweaks
 Terminal=false

settings-dialogs/xfce-workspaces-settings.desktop.in

@@ -2,6 +2,7 @@
 Version=1.0
 _Name=Workspaces
 _Comment=Configure layout, names and margins
+_Keywords=workspaces;settings;preferences;virtual desktops;number;windows;screen;margins;
 Exec=xfwm4-workspace-settings
 Icon=xfce4-workspaces
 Terminal=false