Implementing the move event required to pass the IPC socket to
`i3_ipc_callback_t`, because we won't get notified about any visibility
changes of other workspaces. That's why we query all workspaces again
after a focused workspace was moved.
This is already being done in the initial query response. Not doing it
in the input event handler too leads to an assertion if there are
multiple devices with the same ID.
Hopefully fixes#54
