A static method to provide the unique 128-bit encryption key. 
      Syntax
         
         
            + 
            (
            NSString *
            ) 
            
               getEncryptionKey
            
            : 
            (
            NSError **
            ) 
            error
         
      
      Parameters
         
         
            - 
               error – 
               NSError* object to capture any error if occured during the execution of the method.
            
 
         
       
      Returns
         Returns NSString* a unique 128-bit key to be used for the subsequent operation on DB. 
Usage
       
      Usage
         
         This method should be called at the first invocation of the application to fetch the unique key for the newly created encrypted Database.