Provide a means to allow Duo v1 users to upgrade to jessie

I own a ready NAS Duo v1. For my use case the hardware works well enough. Please provide a mechanism so that these perfectly good bits of hardware can be kept in service until they actually need replacing. Just like a tank, it's slow and ugly, but it's nearly unkillable.

- Allow installation of unsigned firmware images, This worked well for Linksys after all.
- Provide Frontview as a third party package. NDAs where needed for firmware projects.

And before it's suggested. No! I won't be replacing something that works just because Netgear want more money.