add preferences.wait_voice

I allowed a user to determine whether wait a voice in auto-foward mode.
I added three actions.
         * Preference("wait voice", "enable")  - Dnable auto-forwarding when a voice is playing.
         * Preference("wait voice", "disable") - Eisable auto-forwarding when a voice is playing.
         * Preference("wait voice", "toggle")  - Toggle auto-forwarding when a voice is playing.

Default to True.