Renamed all library events to properly seperate out Device and Host mode...

Renamed all library events to properly seperate out Device and Host mode events. Changed the firing conditions for some events to ensure that events are fired by their own USB mode only.

Remove VBUS events - not needed as the library takes care of VBUS detection and feedback on supported AVRs via the USB_Device_Connected and USB_Device_Disconnected events.

Fixed incorrect Host state assignment in the incomplete BluetoothHost demo.