Use PROGMEM and F() properly

Add function to be able to access to strings stored with PROGMEM, it
save 4k memory vs no usage of PROGMEM

esp8266/esp8266.ino

@@ -46,6 +46,7 @@ extern "C" {
 
 void setup() {
   // init :
+  ESP.wdtDisable();
   delay(8000);
   EEPROM.begin(EEPROM_SIZE);
   bool breset_config=false;