Fix default first-time handler

The default first-time handler is defined as a method, but is missing
the 'self' argument in its signature, which causes a run-time error when
it is called.

This only occurs with front-ends that do not install their own
first-time handlers, for instance the shell front-end.
Added high quality download preference.
Added high quality download checkbox.
Added high quality download toggle (YouTube).
Update flashscraper.py
Update flashscraper.py