Add generic name to .desktop file

This often gives the user more information about what kind of
application this is.

vncviewer/vncviewer.desktop.in.in

@@ -1,5 +1,6 @@
 [Desktop Entry]
 Name=TigerVNC Viewer
+GenericName=Remote Desktop Viewer
 Comment=Connect to VNC server and display remote desktop
 Exec=@BIN_DIR@/vncviewer
 Icon=tigervnc