Publish all channels

[furushchev]

• Increase waiting time on USB reset for environments where many usb devices are connected. (it takes longer time)
• Added an option ~main_channel for selecting channel to be used for speech recognition and VAD.
• Added publishers for all 6 channels of respeaker microphone.

Topics are listed as below:

$ rostopic list | grep audio
/audio
/audio/channel0
/audio/channel1
/audio/channel2
/audio/channel3
/audio/channel4
/audio/channel5

If ~main_channel is 0, data published as /audio and /audio/channel0 is the same.