Boolean (checkbox) fields on Team Services

Introduced the ability to add a Boolean (checkbox) field to work item types in Team Services. Detailed the technical challenges in handling the tri-state nature of Booleans (NULL vs. False) and the decision to treat NULL and False values the same in work item and query experiences. Described the field definition, including the sparseness of the Options tab and the default value being False. Outlined the client-specific user experiences for Boolean fields across Web access, Eclipse TEE, various Visual Studio versions, and Excel. Explained the behavior of Boolean fields on existing work items, where un-updated items are treated as False for querying.