Merge pull request #3011 from minrk/kernelclient

IPEP 12: add KernelClient
cleanup IPython handler settings

move settings to the tornado settings dict,
rather than a mixture of tornado settings and application references,
and application.ipython_app references.

removes any reference to application / ipython_app attributes in the handlers,
in favor of the tornado settings dict.
These were a massive pain for anyone who might want to re-use our handlers.