Probability watch face (#69)

* Initial work on probability watch face

* Complete probability watch face

* Restore default movement_config

* PR feedback: PR watch face title, use arc4random, clean up warnings

* Use rand instead of arc4random when building on emulator

* Accidentally overwrote movement_config

movement/movement_faces.h

@@ -52,6 +52,7 @@
 #include "orrery_face.h"
 #include "astronomy_face.h"
 #include "tomato_face.h"
+#include "probability_face.h"
 // New includes go above this line.
 
 #endif // MOVEMENT_FACES_H_