Removed pwmd_get_password(). This has been replaced by pwmd_open_nb()

Removed pwmd_get_password(). This has been replaced by pwmd_open_nb()
and pwmd_save_nb(). These function's will return a file descriptor
that select() can use when a file isn't cached. When available for a
read(), a pwmd_nb_status_t should be read and then passed to
pwmd_open_nb_finalize() or pwmd_save_nb_finalize() to update the pwm
handle.

Renamed pwmd_password_func to pwmd_password_fn and pwmd_status_func to
pwmd_status_fn.

The pwmd_password_fn now requires a pwm_t * argument along with the
void * user data.

No longer include assuan.[ch].