Decide on the metadata we need to store

[sgrieve]

We will need as a minimum:

• bounding box
• spatial reference system
• doi of source data
• doi of paper?
• others?

[ageorgou]

To implement the round-trip transformation as per #9, we will need to write a new file using rasterio, which in turn requires the following fields (http://rasterio.readthedocs.io/en/latest/quickstart.html#opening-a-dataset-in-writing-mode):

• driver
• width
• height
• count
• dtype

The following are listed as optional, so they probably should be recorded to make sure the transformation is correct:

• crs
• transform
• nodata

[ageorgou]

We are currently leaving the nodata field out (see the (code) comments in 1621e45 for details of why).

Note that this shouldn't affect the process, since locations with missing data should be ignored anyway.