Multiple cleanups/tweaks for onewire driver

Use onewire_addr_t for onewire addresses
Move internal defines out of onewire.h
Remove global variables for search state
use taskENTER_CRITICAL instead of portDISABLE_INTERRUPTS
remove unnecessary onewire_init function
Remove unnecessary critical sections
Use GPIO_OUT_OPEN_DRAIN
reformat/style cleanup

examples/ds18b20_onewire/ds18b20_onewire.c

@@ -12,8 +12,6 @@
 
 // DS18B20 driver
 #include "ds18b20/ds18b20.h"
-// Onewire init
-#include "onewire/onewire.h"
  
 void print_temperature(void *pvParameters)
 {
@@ -26,8 +24,6 @@ void print_temperature(void *pvParameters)
     // Use GPIO 13 as one wire pin. 
     uint8_t GPIO_FOR_ONE_WIRE = 13;
     
-    onewire_init(GPIO_FOR_ONE_WIRE);
-    
     while(1) {
         // Search all DS18B20, return its amount and feed 't' structure with result data.
         amount = ds18b20_read_all(GPIO_FOR_ONE_WIRE, t);