Restructured behaviour for improved multiuser compatibility

The behaviour of the previous testing versions was restructured completely in this version to allow script to run properly on multi user systems. User specific locale for write-out-global are not implemented still. Some confusing and conflicting config-file options have been removed or modified.

Important: This version expects to have the symbolic links in users homes pointing to:

/home/<username>/.fluxbox/menu-applications -->  /usr/share/desktop-menu/<username>/.fluxbox/menu-applications
/home/<username>/.icewm/menu-applications -->  /usr/share/desktop-menu/<username>/.icewm/menu-applications
/home/<username>/.jwm/menu-applications -->  /usr/share/desktop-menu/<username>/.jwm/menu-applications

Otherwise it won't work properly. Need to get set accordingly also in /etc/skel.

an additional OS default settings file is expected which is used by --write-out-global as long a user has no private config file created.

Backward compatibility to apt-hook is kept, but --write-out-global needs to be run sudoed now (since it will perform a system wide update of menus). No additional command line options are accepted when --write-out-global is filed, but this is implemented error tolerant, so it will execute anyway, ignoring all additional options from command line.

New option --write-out-single works mostly the same as --write-out-global, but only for logged in user, and it accepts additional command line options and allows storing the options to user config file.

Added file permissions and ownership correction of written menu files in case script was run sudoed, so the user can write to them still when calling the script unsudoed later.