Dashboard: Order Open Invoices by duration open

[colindean]

Maybe even shade a date by how long it's been open.

E.g. #FEE Light pink for 2 weeks open -> #F00 blinking red for 2 months open.

[jtgeibel]

I couldn't find an easy way to add a color scheme, but I think it looks a lot better already. The time is included in an html5 time tag so it probably wouldn't be hard to do something in jQuery, but I don't have the time to look into it right now.