Add units to meta file

[DominicOram]

See DiamondLightSource/ADOdin#22

• Requires Add the ability to specify attributes on HDF5Datasets odin-detector/odin-data#351. Merge this first then we need to unpin here

To test:

• Run test_file_write
• Open the created file and confirm that unit attributes are provided on the datasets in the issue

[GDYendell]

Pin removed now odin-detector/odin-data#351 merged

[GDYendell]

There are some datasets missing units (e.g. frame time, wavelength), but I guess you have added all the ones you need?

[DominicOram]

Yh, I added everything I needed and a few of the more obvious ones. I didn't go through and check every field though, I'm happy to go back and do frame time and wavelength for completeness

[GDYendell]

I think having just a few of them missing could be confusing, so we should add them all now that you have done most of them.

[DominicOram]

Ok, I have added some more, I think that's all of them now. For future reference I used https://media.dectris.com/NeXus_Groups_API_1.3.pdf to work out the units when I was unsure.