Proposed plugin to add entry to desktop menu

[trumpton]

I've created a plugin which installs an app-hook script.
This checks the command line parameters, and if --install-desktop is provided, the script copies the .desktop and icon into the user's local menu config area, or the system one (if run by root), and modifies the Exec so that the AppImage is executed.

./MyApplication.AppImage --install-desktop
will add the AppImage application to the start menu for the current user.

linuxdeploy-plugin-installdesktop.txt

[TheAssassin]

Please file a pull request so we can leave review comments.