[PCF7930] Refactoring & bugfix in READING

firs commit of a few to come.
First renames of variables, added a few comments to improve clarity.
Fixed types (int -> unitx_t , const, ...) - not all. still some to come

Fixed 2 conditions that did not work properly. Here some explanation:

  Imagine dest[i-1] = 255 and dest[i] = 0. THis would mean a clear falling edge.
  However, this code would not work, since dest[i] > lmax is not true.
  This condition only works if I have at least 1 sample between lmax and 255.
  Same for the other way around.

armsrc/pcf7931.h

@@ -18,6 +18,13 @@
 
 #include "common.h"
 
+
+typedef enum{
+    UNDEFINED,
+    FALLING,
+    RISING 
+} EdgeType;
+
 size_t DemodPCF7931(uint8_t **outBlocks, bool ledcontrol);
 bool IsBlock0PCF7931(uint8_t *block);
 bool IsBlock1PCF7931(const uint8_t *block);