Remove spaces from atomic recipe name in multivariable atomic recipes
Addresses #219 (closed)
Recipe splitting does not work for multivariable atomic recipes because the atomic recipe name has spaces and/or commas in it, e.g. atomic_recipe_sys-ECMWF-SEAS51_ref-ERA5_var-tas hurs_reg-EU_sdate-0601.yml
This MR changes tools/divide_recipe.R to replace the spaces in the variable with dashes.