lorawan cleanup and optimizations:

- Remove all default loraconf default initialisation in lorawan examples (Region Settings takes care of this now)
- Remove retries while receiving JoinAccept and increase LoraRX to 10s (no need to wait more than 10s)
- Add constants for RegionSetting default frequencies
- Standardize all lora default configurations in lora examples
- Add new AT+LW=NET,(ON|OFF) command in atcmd example

lora/radio.go

@@ -12,5 +12,8 @@ type Radio interface {
 	SetSpreadingFactor(sf uint8)
 	SetPreambleLength(plen uint16)
 	SetTxPower(txpow int8)
+	SetSyncWord(syncWord uint16)
+	SetPublicNetwork(enable bool)
+	SetHeaderType(headerType uint8)
 	LoraConfig(cnf Config)
 }