util: Add ni_var_array_remove() and ni_var_array_remove_at()
xml: Add xml_node_del_attr() utility
xml: Fix functions retrieving numerical attr values
util: add "yes|no" to ni_parse_boolean()
ifstatus: Do not consider client-state in ifstatus

Rename status NOT_STARTED to UNCONFIGURED
Cherry-picked commits from pwieczorkiewicz:client-state

Signed-off-by: Marius Tomaschewski <mt@suse.de>