nc-update-nextcloud: only try to restore on reboot once

ncp-web: fix section unselected when sidebar reloads

ncp-web: escape HTML in details box

upgrade to NC15

wizard: dont change missing parameters

nc-update-nc: remove backup after restoring

ncp-config: allow empty values

ncp-web: new chinese translate and update chinese translate. (nextclo…

…ud#721)

curl installer: add provisioning step

dynDNS: pdate cron execution interval (nextcloud#754)