Misc bugs mostly GloFAS

[turnerm]

Some small things to fix that I found while working with GloFAS data:

• [x] related to #179, give a warning if users have more than 500 requests, advise them to split up into two instances
• [x] add "Sleeping for 1 minute.." when that is happening during the download queue
• [x] check_file_existence shouldn't exclusively use the terminology "downloading" because it's also applied to processing
• [x] bug in the final list of commands of GloFAS docs
• [x] set COD AB default to be admin 0 (as is stated in the documentation)