Implement fetching prices for time range in Online Quotes

This patch allows to download currency exchange rates and stock prices
for settable time period at once. It uses CSV Importer if time range is
not current day and old routine if time range is current day.
There is feature to dump CSV profile used for importing prices and to
customize it.
There is policy configuration dialog for updating prices, so that e.g.
no manually entered price gets overridden by Online Quotes.

Differential Revision: https://phabricator.kde.org/D5925