luci-app-openvpn: remove obsolete config options

* remove obsolete config options according to
  openwrt/openwrt@89b8ba9

, fix for #2135
* whitespace/intendation fixes
* replace fieldset leftover with div
* fix finally recipe options transfer to regular config with "Add"

Signed-off-by: Dirk Brenken <dev@brenken.org>