buildroot

package: new category for fonts, icons, sounds and themes

Move all of the scattered fonts, icons, sound packs and themes into a
new category for them.
In preparation for the inclusion of more fonts.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>