Add button to download CSV
Added CSV format to markers
Avoid unclear exception when trying to download empty CSV
Fix CSV download button and marker list CSS
Fix typo
Hide download CSV button until we're sure it works fine
Revert "Hide download CSV button until we're sure it works fine"

This reverts commit b582ca5c7b4b06316a5a227aaba42d93a3aa8fe3.
Set content type for CSV download to CSV

Otherwise Safari downloads it with an HTML suffix.
Fix sidebar marker list bottom to now overlap with CSV button