First cut at allowing the kernel to be restarted from the frontend.

Reimplemented IPythonWidget's edit magic handling to support line numbers. Also, removed the code path for launching the file with the system default Python application, as this is too dangerous.

Minor cleanup (again).

Fixed minor bug in last checkin.

The FrontendWidget now performs tab-completion more aggressively.

Fixed bug introduced by the recent payload processing refactor.

Fixed bug where replacement prompts were occasionally inserted at inappropriate times.

* Added support for prompt and history requests to the kernel manager and Qt console frontend. * Updated message spec to be consistent with the IPython kernel implementation.

The ConsoleWidget now only pages text if it exceeds the height of the visible window.

Fixed bug where the banner message was syntax highlighted when the frontend connected to a new kernel.