Added zsh and oh my zsh, and enabling it as default for new users

files/scripts/installohmyzsh.sh

@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+
+# Tell build process to exit if there are any errors.
+set -oue pipefail
+
+git clone https://github.com/ohmyzsh/ohmyzsh.git /usr/share/ohmyzsh

files/system/etc/default/useradd

@@ -0,0 +1,8 @@
+# useradd defaults file
+GROUP=100
+HOME=/home
+INACTIVE=-1
+EXPIRE=
+SHELL=/bin/zsh
+SKEL=/etc/skel
+CREATE_MAIL_SPOOL=yes