* Add support for declaring a BuyPrice and BuyCurrency in portfolio.
eg: ["Algorand", "125.4", "0.8", "USD"]
Add optional (default off) columns to portfolio:
"buy_price", "buy_currency", "profit", "profit_percent"
Note: there is no UI for entering this yet.
* Use exchange-rates to convert GlobalMarketGraphData
* Ask for global data in usd just in case it starts working again :)
* Include currency conversion in chart title #207
* Better error handling
* Redundant type conversions
* Remove redudant type declarations. Inline one-line constructors. Remove unnecessary brackets.
* Simplify name - it's used via package name anyway
* Simplify variable initializations
* Change `var x uint = Y` to `x := uint(Y)`
* More shorthand initialization