Add global stats to logged out homepage

Here is a screenshot of what this looks like. The screenshot does not include the fix to add `|number:2` to the `executedSellBTCSum`. I am not very good at making things pretty, so feel free to format however you want.  There are additional statistics available on the `$globalStats` object, as defined by the columns in the query inside `OrdersModels->calculateOrderStats()`.

![screen shot 2014-03-04 at 5 20 05 pm](https://f.cloud.github.com/assets/2415796/2328676/615efbd4-a404-11e3-9c38-dfb7581bb102.png)