Support descending/multiple string ordering

E.g.,

  // Descending
  [Person order:@"firstName DESC"];

  // Multiple
  [Person order:@"lastName, firstName"];

  // Multiple, descending
  [Person order:@"lastName DESC, firstName DESC"];

Signed-off-by: Stephen Celis <stephen@stephencelis.com>
Update Kiwi specs to use @() over theValue()

64-bit support.

Signed-off-by: Stephen Celis <stephen@stephencelis.com>
Update Specs

 - Update to Kiwi 2.2.4
 - Update to us XCTest

Signed-off-by: Stephen Celis <stephen@stephencelis.com>