masterpdfeditor: move assets into $out/opt/masterpdfeditor, symlink from $out/bin

pkgs/applications/misc/masterpdfeditor/default.nix

···
       ];
       dontStrip = true;
       installPhase = ''
-        mkdir -p $out/bin $out/share/applications $out/share/pixmaps
+        p=$out/opt/masterpdfeditor
+        mkdir -p $out/bin $p $out/share/applications $out/share/pixmaps
 
         substituteInPlace masterpdfeditor4.desktop \
           --replace 'Exec=/opt/master-pdf-editor-4' "Exec=$out/bin" \
           --replace 'Path=/opt/master-pdf-editor-4' "Path=$out/bin" \
           --replace 'Icon=/opt/master-pdf-editor-4' "Icon=$out/share/pixmaps"
-
-        cp -v masterpdfeditor4 $out/bin/masterpdfeditor4
         cp -v masterpdfeditor4.png $out/share/pixmaps/
         cp -v masterpdfeditor4.desktop $out/share/applications
 
-        cp -v -r stamps $out/bin/stamps
-        cp -v -r templates $out/bin/templates
-        cp -v -r lang $out/bin/lang
-        cp -v -r fonts $out/bin/fonts
+        cp -v masterpdfeditor4 $p/
+        ln -s $p/masterpdfeditor4 $out/bin/masterpdfeditor4
+        cp -v -r stamps templates lang fonts $p
+
         install -D license.txt $out/share/$name/LICENSE
 
         patchelf --interpreter "$(cat $NIX_CC/nix-support/dynamic-linker)" \
                  --set-rpath $libPath \
-                 $out/bin/masterpdfeditor4
+                 $p/masterpdfeditor4
       '';
       meta = with stdenv.lib; {
         description = "Master PDF Editor";