Added comments to openvpn.nsi

Signed-off-by: Samuli Seppänen <samuli@openvpn.net>
Removed unused FileFunc.nsh from openvpn.nsi

Signed-off-by: Samuli Seppänen <samuli@openvpn.net>
Fixed a bug preventing silent installations to non-standard directories

Trac-ticket: 249
Signed-off-by: Samuli Seppänen <samuli@openvpn.net>
Added and fixed documentation links in openvpn.nsi

Signed-off-by: Samuli Seppänen <samuli@openvpn.net>
Updated build variables to match openvpn-2.3.0 build I004

Signed-off-by: Samuli Seppänen <samuli@openvpn.net>