New filter request

[Doug Boling]

One of the best features of Kanbanize is the ability to add custom fields. However, these fields can not be used in the board filter to limit the all the tasks one is looking at.  The ability to do so using the "search field" at the top of the screen is perfect but it does not directly interact with the board.  Please consider adding the ability to add a custom fields to the board filter.  It would be great to add as many as we can just like in the search dialog box.