tsherwen/sparse2spatial: Initial release of code for preparing sea-surface iodide obs. file

This release follows updates to the code used for processing iodide sea-surface observations. Scripts have been added to enable incorporating new data (as it becomes available) into the dataset archived with British Oceanographic Data Centre (BODC). These updates were made following comments from peer-review of the observational iodide sea-surface dataset's data descriptor manuscript.

Only the code associated with preparing the current observational dataset and adding new observations should be considered production-ready. This is still subject to change based on editoral decisions following responses to reviewers. This repository also contains code under development for other subsequent projects, such as using the observational sea-surface iodide data for predicted a spatially and temporally resolved global dataset. Please use later releases if these are available.

Reference for archived data: Chance R.; Tinel L.; Sherwen T.; Baker A.; Bell T.; Brindle J.; Campos M.L.A.M.; Croot P.; Ducklow H.; He P.; Hoogakker B.; Hopkins F.E.; Hughes C.; Jickells T.; Loades D.; Reyes Macaya D.A.; Mahajan A.S.; Malin G.; Phillips D.P.; Sinha A.K.; Sarkar A.; Roberts I.J.; Roy R.; Song X.; Winklebauer H.A.; Wuttig K.; Yang M.; Zhou P.; Carpenter L.J.(2019). Global sea-surface iodide observations, 1967-2018. British Oceanographic Data Centre - Natural Environment Research Council, UK. doi:10/czhx.