title: Populating <validuser/> field in WorkItem
body: <p>I've created a new WorkItem named Project that contains a field named business owner which can be any domain user.</p>
  
  <p>The field was created using the WorkItem XML syntax using the  tag. I have a problem that only TFS valid users (as the name suggests :)) show up the the combobox in the Visual Studio form.</p>
  
  <p>Is there any way for me to let that box contain all domain users without having to give all users some tfs read access ? If not then what is the minimum access that I can apply in TFS that I can give to all domain users ? Or is there some other way that I can't notice ?</p>