Qt console doesn't handle the `--gui` flag correctly.

[fperez]

We should pass it to the kernels just like we support --pylab at startup.

[mwiebe]

There's something wrong with how this interacts with the notebook, too. I'm finding that if I restart the kernel in the notebook, I have to explicitly say '%gui qt' even if I gave it as a command line option to start.

[minrk]

This was closed by #1707