v1.6 RC release

updates since v1.5:
kiss-vm:
fix vm delete fail: add --nvram option to virsh undefine
add --postrepo option
separate distro-db from kiss-vm -> /etc/kiss-vm/distro-db.bash
add --virt-install-opts option
add bash-completion for kiss-vm
workaround of performance issue in pek lab
add sub-command help,h
add one more example script: rh-training-lab.sh
split the sub-command 'net' to 'netls' and 'netcreate'
export and add usage info of sub-commands: cpfrom and cpto
add new sub-commands prepare,enable-nested-vm

utils:
add commands addipvlan,addnetns,addvrf,addif2netns,addif2br-vrf-and-so-on