Update NUT submodule to v2.7.2
projects: update walNUT description

As of walNUT's e396caa93db28680564ff69b820830857d08a046, it doesn't rely any longer on ups{c,cmd,rw}, but uses instead a GJS implementation of NUT's net protocol.
Update NUT submodule
Add mge-usb-rj45.jpg to the list of cable images

As per NUT's fe04d7d46eee507d6c46f79320a853f024cff3a2
Update projects.txt

Added python-nut2 and webNUT to "Other software projects" section.
Add DDL generation

Add raw DDL as a submodule (ddl)
Add DDL generation tool and process
hcl: link also to DDL (manufacturer, model)

Both in static (python) and dynamic (JS) HCL, link to DDL manufacturers and models.
Fix dependencies of HCL.
hcl: simplify merging of rows with same driver and support-level (JS)
ddl: add compatibility with old versions of make

$(file ...) function is available in make only starting from 3.82.90:
http://git.savannah.gnu.org/cgit/make.git/commit/?id=fca11f60390cf607f68b497c3909b1fb40251070
Therefore, rework the file creation to call a 'file' 'function' (i.e. variable 'file') if the built-in file function is not available.
ddl: update submodule (README.adoc to be usable on GitHub)
ddl: make sure items are sorted correctly
hcl: cosmetic changes (python)
hcl: minor cleanup (python)

Remove unused imported modules and exception.
hcl: move data fields definition to be a global setting (python)
hcl: simplify merging of rows with same driver and support-level (python)
ddl: ignore case when sorting items
ddl: be even less verbose by default
ddl: move retrieving info from filename before processing the file
ddl: support also commented RW/CMD declarations for .dev files
ddl: take into account also files with shell-unfriendly names