Updated openvpn app to work with current openvpn package

Signed-off-by: Vladimir Ulrich <admin@evl.su>
Added device tree model support

Signed-off-by: Vladimir Ulrich <admin@evl.su>
Fixed pinghost to pinghosts

Signed-off-by: Vladimir Ulrich <admin@evl.su>
Merge pull request #220 from Wedmer/openvpnfix_dtfix_watchcatfix

 applications/luci-openvpn: fixes for current openWRT openvpn packages.