alsa-utils: moved to /sound and Sound category, fix minor bugs

Moved source folder in /sound folder, and changed all packages in the makefile
to be shown in Sound category (not in Sound subcategory of Utilities).
Removed a line calling a non-existent Package/alsa-utils/Default
and site URL to the package alsa-utils-tests.

Signed-off-by: Alberto Bursi <alberto.bursi@outlook.it>