API Lifecycle Implementation, Part 2 (#217)

* additon of 'get_mnemonic' API function

* rustfmt

* added 'change_password' api function

* rustfmt

* add 'delete_wallet' function'

* rustfmt

tests/common/mod.rs

@@ -405,8 +405,8 @@ where
 				let value: OUT = v;
 				Ok(Ok(value))
 			}
-			Err(e) => {
-				println!("Error deserializing: {:?}", e);
+			Err(_) => {
+				//println!("Error deserializing: {:?}", e);
 				let value: OUT = serde_json::from_value(json!("Null")).unwrap();
 				Ok(Ok(value))
 			}