[board] Implement a u16 based Move

Replace building a Move with the Move struct itself with a MoveBuilder that
builds a Move and returns it.

Update the tests and move formatter.

board/src/position/mod.rs

@@ -3,6 +3,7 @@
 mod diagram_formatter;
 mod flags;
 mod pieces;
+#[macro_use]
 mod position;
 
 pub use diagram_formatter::DiagramFormatter;