NimBLEAddress: New constructor added to create blank addresses

* Docuement NimBLEAddress::getNative in migration docs.

Author: h2zero

docs/Migration_guide.md

@@ -47,6 +47,12 @@ For example `BLEAddress addr(11:22:33:44:55:66, 1)` will create the address obje
 
 As this paramameter is optional no changes to existing code are needed, it is mentioned here for information.  
 <br/>
+`BLEAddress::getNative` (`NimBLEAddress::getNative`) returns a uint8_t pointer to the native address byte array.  
+In this library the address bytes are stored in reverse order from the original library. This is due to the way  
+the NimBLE stack expects addresses to be presented to it. All other functions such as `toString` are  
+not affected as the endian change is made within them.  
+<br/>
+
 <a name="server-api"></a>
 ## Server API
 Creating a `BLEServer` instance is the same as original, no changes required.

src/NimBLEAddress.cpp

@@ -37,6 +37,14 @@ NimBLEAddress::NimBLEAddress(ble_addr_t address) {
 } // NimBLEAddress
 
 
+/**
+ * @brief Create a blank address, i.e. 00:00:00:00:00:00, type 0.
+ */
+NimBLEAddress::NimBLEAddress() {
+    NimBLEAddress("");
+} // NimBLEAddress
+
+
 /**
  * @brief Create an address from a hex string
  *

src/NimBLEAddress.h

@@ -33,6 +33,7 @@
  */
 class NimBLEAddress {
 public:
+    NimBLEAddress();
     NimBLEAddress(ble_addr_t address);
     NimBLEAddress(uint8_t address[6], uint8_t type = BLE_ADDR_PUBLIC);
     NimBLEAddress(const std::string &stringAddress, uint8_t type = BLE_ADDR_PUBLIC);