chroot: add option to prevent removal of ssh keys
chroot: add option to package rootfs into directory
allow working directory to be different than project directory
Merge branch 'keep_ssh_keys' of https://github.com/jlefley/omap-image-builder
Merge branch 'use_oib_root' of https://github.com/jlefley/omap-image-builder
publish: use --bbb-old-bootloader-in-emmc for all bone images and update server dir

Signed-off-by: Robert Nelson <robertcnelson@gmail.com>