Clean up / organize ALF directory

We could try to slim down a bit ALF's installation directory.

Currently we have, typically:

Analysis
CHANGELOG.md
CITATION
CITATION.cff
COMMUNITY.md
configure.sh
Documentation
doxygen
get_compiler_version.F90
gitintro.pdf
HDF5
Images
Libraries
license.additional
license.gpl
license.lapack
Makefile
Mathematica
Prog
README.md
roadmap.md
Scripts_and_Parameters_files
testsuite

One possibility is to group a few of those, e.g.:

• Code (new): containing Analysis, HDF5, Libraries, Prog, testsuite and Hamiltonians (if we follow issue #204 (closed) and move Hamiltonians out of Prog)
• Tools (new): containing gitintro.pdf, Mathematica, get_compiler_version.F90, and Scripts (Scripts_and_Parameters_files minus Start, to be moved to base directory)
• Documentation: include doxygen and Images in it

This way we'd end up with:

CHANGELOG.md
CITATION
CITATION.cff
Code
COMMUNITY.md
configure.sh
Documentation
license.additional
license.gpl
license.lapack
Makefile
README.md
roadmap.md
Start
Tools