Update desktop specific default apps

- Remove xpdf  
- Remove gnome-brave-icon-theme from kali-desktop-gnome  
- Add lightdm-gtk-greeter-settings to kali-desktop-mate and  
  kali-desktop-xfce so that the user is able to modify the  
  login background.  
- Add blueman to kali-desktop-mate and kali-desktop-xfce  
- Ensure all kali-desktop-* packages include the following  
  util apps by default:  
  
* Image viewer  
* Video player  
* Archiver  
* Terminal  
* Editor  
* Calculator  
* PDF viewer  
* Task manager  
* Screenshot tool  
* Video recorder  
  
Xfce  
  Image viewer: ristretto  
  Video player: parole  
  Archiver: engrampa  
  Terminal: qterminal  
  Editor: mousepad  
  Calculator: mate-calc  
  PDF viewer: atril  
  Task manager: xfce4-taskmanager  
  Screenshot tool: xfce4-screenshooter  
  Video recorder: kazam  
  
  Other:  
    lightdm-gtk-greeter-settings  
    blueman  
  
GNOME  
  Image viewer: eog  
  Video player: totem  
  Archiver: file-roller  
  Terminal: gnome-terminal | gnome-terminal  
  Editor: gedit  
  Calculator: gnome-calculator  
  PDF viewer: evince  
  Task manager: gnome-system-monitor  
  Screenshot tool: gnome-screenshot  
  Video recorder: gnome-shell-extension-easyscreencast  
  
KDE  
  Image viewer: gwenview  
  Video player: vlc  
  Archiver: ark  
  Terminal: konsole  
  Editor: kwrite  
  Calculator: kcalc  
  PDF viewer: okular  
  Task manager: ksysguard  
  Screenshot tool: kde-spectacle  
  Video recorder: simplescreenrecorder  
  
MATE  
  Image viewer: eom  
  Video player: parole  
  Archiver: engrampa  
  Terminal: qterminal  
  Editor: pluma  
  Calculator: mate-calc  
  PDF viewer: atril  
  Task manager: mate-system-monitor  
  Screenshot tool: mate-utils # mate-screenshot  
  Video recorder: kazam  
  
  Other:  
    lightdm-gtk-greeter-settings 
    blueman