Comment 19 for bug 1377566

I've done more work on this and I think I'm very close to finished. (Basic error handling turned out to be straightforward enough in hindsight)

At this point I need a little help:

1. I'd like the comments text box in the properties dialog to have scroll a vertical scroll widgets. I've struggled to figure out how to do that (and regret ever writing UI code in GTK, learning how to integrate generated .ui files can't be much worse than this was).

2. I'm happy with my method to convert from pixels to centimetres (and I don't think it is actually important) but since it was one of the first things that you asked me to correct I have tried and failed to figure out how exactly I'm supposed to get the DPI

Aside from that I'm happy with the code, I've improved the OpenRaster support, I've been strict and included a manifest, and I've extended OpenRaster to include metadata in the same way as OpenDocument.