Fix minor style issues in StockSource/StockWidget

This pull request fixes some minor style issues in StockSource and StockWidget. Most are whitespace-issues, but some unused code is also removed.
We're not very consistent on that matter. Very specific widgets either have (`BuildWidget`) or don't have (`ScrumWidget`) a default title.

I agree on having a default title on widgets that are tied with a very specific source, as is the case of this one.