Refactor recording api methods and fix logic

Refactored code of recording api setup, teardown, and
endpoint functions.

Added a get_current_state_str() method to Multimedia to make some code
in recording api cleaner.

Fix to recording api logic determining next_id.
Fix to test_server.py teardown to undo patching to media_dict
I wonder if this is useful at all? [do_teardown_appcontext](http://flask.pocoo.org/docs/0.10/api/#flask.Flask.do_teardown_appcontext).