Fixed addition and removal of stocks from the portfolio.
Avoided getters inside the models.
Exercise 7: Replaced constants with an enum.
Exericse 7: Added balance to portfolio.
Refactored removal of stocks.
Made it possible to remove stocks by their index.
Added and fixed documentation.
Exericise 7: Added functions to buy and sell stocks, fixed
documentation.
Exercise 7: Added additional get functions to the portfolio.
Exercise 7: Updated portfolio's HTML representation.
Minor style fix.
Fixed stock removal.
Fixed a typo.
Fixed portfolio's copy-constructor.
Exercise 7: Updated portfolio's output.
Fixed purchasing stocks and changed output.