read-dev-usbmon: prepend time to message
ltunify: introduce read timeouts

In case a message does not get a response (user pulled out the receiver,
thunder hit the device, coke has fallen on a keyboard, etc.), do not wait
`for(;;)`. (2 seconds because accessing registers may be slow)
ltunify: show HID++ version
hidraw: annotate HID++ 2.0 errors and IRoot feature
ltunify: preliminary HID++ 2.0 support, add TODO