replace libraries which are no longer supported

[jrhillae]

@SanderDevisscher: I replaced all rgdal functions with sf. I have one warning remaining when running the file 8_baseline_maps_ui_D1.R but it is not clear to me how to solve it:

Input to asJSON(keep_vec_names=TRUE) is a named vector. In a future version of jsonlite, this option will not be supported, and named vectors will be translated into arrays instead of objects. If you want JSON object output, please use a named list instead. See ?toJSON.

It is related to this part of the code as the warning is reprinted each time the distribution map is refreshed. A stackoverflow issue related to this warning can be found here, but printing the output instead of returning it did not solve it (as suggested in the issue).

Do you have a suggestion on how to solve this? Thank you!