Exchangerates.host has switched to a paid service. There aren't a lot of good free alternatives.

There are numerous places that we can download CSV data. For example Forexsb offers detailed CSV files for free if you sign for a free account. I propose we modify the forex function to make use of CSVs as a backup.

What we could do is build a graph without prices and when missing prices are found, the user is alerted to download CSV files and put them in the cache folder. We can make use of more detailed information, but for now, only daily candles will be supported. That should be easy to work with since that is only around 5000 candles since 2008.