Changes to smart_device

1) Undo setting _debug as synchronized. It was already synchronized inside itself, and adding the wrapper broke getting the correct method name.
2) Import the date methods once.
3) Make date_read sync'able in both directions

If you find reason to make a point release, that would help me. Reason: the backed-out change (#1) fixes a problem where smart_device logs are very hard to read because the method names are gone. This isn't urgent.