Fix missing documentation for many clock faces:

* Move from .c to .h as needed for consistency.
* When missing from both, copy from pull request or wiki.
* When missing entirely, infer functionality from source code.

movement/watch_faces/complication/ratemeter_face.h

@@ -25,6 +25,16 @@
 #ifndef RATEMETER_FACE_H_
 #define RATEMETER_FACE_H_
 
+/*
+ * RATE METER face
+ *
+ * The rate meter shows the rate per minute at which the ALARM button is
+ * being pressed. This is particularly useful in sports where cadence
+ * tracking is useful. For instance, rowing coaches often use a dedicated
+ * rate meter - clicking the rate button each time the crew puts their oars
+ * in the water to see the rate (strokes per minute) on the rate meter.
+ */
+
 #include "movement.h"
 
 typedef struct {