Some fields do not show up in Vertical lane or Swimlane field in Visual Task Board

When creating a Data Driven Visual Task board, some fields that are available on the form are not available in vertical lane and swimlane.

Steps to reproduce:

1. Create a new Visual Task Board
2. Select Data Driven Board
3. Task Table: Demand
     Vertical Lane Field: Assigned To
     Swimlane Field: Order

Notice Order fields is not available in the list:

Confirmed on New York and Orlando

For the selection of the Vertical lane field and Swimlane Field, we show only those fields from the table which will be either choice field or reference field.

In this case, order is neither a choice field nor a reference field, hence we can not create VTB on it.

If a field is not available that is required for vertical lane or swimlane,  it would need to be made into a choice field.  This will require one to create all available choices for that field.