gtkf-sketcher should be installed by sudo make install

[vmagnin]

Describe the bug
gtkf-sketcher.f90 (and the needed tools and files, like usemodules.py) should be installed by $ sudo make install instead of being launchable from the build directory.

Expected behavior
The user should be able to call gtkf-sketcher as a command.

Your system:

• GTK branch: gtk3 and gtk4 (gtk2 is now obsolete)

Additional context
If we want to be able to install several branches, e.g. gtk-3-fortran and gtk-4-fortran, we should name the tool accordingly: gtkf-3-sketcher, gtk3f-sketcher, gtkf-sketcher3 ? The first idea would me more coherent with the package name.

[vmagnin]

See #213

The configuration file "default.options" still needs to be located in the working directory and needs to be writable. I recommend - as future work - making default.options into a dotfile that can be saved in the user's home directory, or something like that.