Config files can now be merged from 4 sources:  distribution-provided,
(share folder), local (/etc/saturnin), user-specific (~/.saturnin and
~/saturnin/ini.d/*)

Paths are transferred by saturnin meta-command so there's no need
to build sub-command binaries

Move cub-command to libexec path to prevent calling them directly,
allowing for better control of environment.

Fortify against bad characters in URLs.  This also makes www print one
URI per line (which was intended in the first place).

Scripts are supposed to be launched as sub-commands of /bin/saturnin, which
can easily handle this for them.

Or you can still set these variables by hand.  (i.e. `FFOO_DEBUG=true saturnin-www`)

Avoids need to replace __EECC_INI__PATH

Increase readability: decrease complexity of the build function and
preserve wandering off too much against 80-char "buoy"

Make it easier to share &  sync installer code across projects from the
same family.