Separate base packages from customizations

The `build.packages` and `install.packages` files in the CONFIGDIR now
only need to include *additional* packages to install.  The packages
*required* for Aimee OS are always installed, listed in the
corresponding files in the source directory.

yellow/build.packages

@@ -1,3 +1 @@
 sys-boot/grub
-sys-boot/raspberrypi-firmware
-sys-boot/u-boot

yellow/host-tools.packages

@@ -1,9 +0,0 @@
-sec-policy/selinux-base
-sys-apps/policycoreutils
-sys-apps/systemd
-sys-boot/grub
-sys-fs/btrfs-progs
-sys-fs/dosfstools
-sys-fs/genimage
-sys-fs/mtools
-sys-fs/squashfs-tools

yellow/install.packages

@@ -1,6 +0,0 @@
-net-misc/openssh
-net-misc/wget
-sec-policy/selinux-aimee-os
-sys-apps/busybox
-sys-apps/systemd
-sys-fs/btrfs-progs