Mission item: CONDITION_YAW -use shortest direction by default

This defaults to the most obvious way to turn (shortest direction) from
commit Mission item: CONDITION_YAW - added shortest direction.
This behaviour when changing directions is what users are familiar with
from any simple mission flight (that RPAS turns the shortest way toward
the target)

src/MissionManager/MavCmdInfoCommon.json

@@ -463,8 +463,8 @@
             },
             "param3": {
                 "label":            "Direction",
-                "enumStrings":      "Clockwise,Counter-Clockwise",
-                "enumValues":       "1,-1",
+                "enumStrings":      "Clockwise,Shortest,Counter-Clockwise",
+                "enumValues":       "1,0,-1",
                 "default":          1
             },
             "param4": {