changed the modules to use the new BACNet string types.

Modified the device object to handle having the string properties changed via WriteProperty service.
Updated the unit tests.
Updated the demo objects.

bacnet-stack/awf.h

@@ -55,11 +55,7 @@ typedef struct BACnet_Atomic_Write_File_Data
       unsigned returnedRecordCount;
     } record;
   } type;
-  // note: set the file data to an empty buffer
-  // and set the DataLength to the size of the empty buffer
-  // before decoding the data.
-  uint8_t *fileData;
-  unsigned fileDataLength;
+  BACNET_OCTET_STRING fileData;
 } BACNET_ATOMIC_WRITE_FILE_DATA;
 
 #ifdef __cplusplus