Support trees with categories started not with "core/base/extra" for easier external tree support (linux-kernel-extra, aosc-os-arm-bsps, etc)

[Icenowy]

root@e531 [ acbs@staging ] # cat /etc/acbs/forest.conf 
[default]
location = /usr/lib/acbs/repo

[linux-kernel-extra]
location = /var/lib/acbs/linux-kernel-extra
root@e531 [ acbs@staging ] # ls /var/lib/acbs/linux-kernel-extra
featured-kernel  machine-kernel  march-kernel  README.md  upcoming-kernel
root@e531 [ acbs@staging ] # ls /var/lib/acbs/linux-kernel-extra/upcoming-kernel/
linux-next
root@e531 [ acbs@staging ] # cat /var/lib/acbs/linux-kernel-extra/upcoming-kernel/linux-next/autobuild/defines 
PKGNAME=linux-next
PKGSEC=kernel
PKGDEP=""
BUILDDEP="bc dracut git"
if [[ "${CROSS:-$ARCH}" = "amd64" ]]; then
    BUILDDEP+=" grub"
fi
PKGDES="linux-next branch, use at your own risk."

ABSTRIP=no
ABELFDEP=no
ABRPMAUTOPROVONLY=yes
root@e531 [ acbs@staging ] # ./acbs-build.py -t linux-kernel-extra linux-next
-----------------------------------------------------------------------------------Welcome to ACBS - 20170104-----------------------------------------------------------------------------------

[CRIT]: Oops! ACBSGeneralError: No valid candidate package found for linux-next.

[MingcongBai]

Due to performance concerns, you could only build trees with base-*, core-*, and extra-* categories.

[liushuyu]

This has been fixed

[MingcongBai]

Where?