Added Unknown mode

[agusalex]

On the Asset Allocation page when some assets are not recognized by sector or country, it cant get pretty hard to understand the distribution of things. It is particularly annoying with cash, since it is common to have some amount of it, and this would cause the countries to chart and the sector chart to show UNKNOWN as a type.

This is what got changed to remediate this issue:

• Added ETF support to Yahoo provider so that ETFs get properly populated on the sector and country chart
• Added Unkown Mode to users decide if they want to view an accurate chart of sector and country or a cleaner one that shows the data that's relevant, this way we don't sacrifice precision or ease of use.
• Set Unknown mode to default ON ( same behavior as before ) and it is the user's choice to disable it. It's my opinion the platform looks better with it off but I didn't want to disrupt previous behavior.