GUI-352: Inline Create Key Pair operation for Launch Instance wizard

Inline operation to create a key pair for the Launch Instance wizard.  The newly-created key pair is immediately added to the key pair choices and is selected by default.

Note: We're displaying the key instead of downloading it for two reasons…

1. Downloading via an XHR response without redirecting to a whole new page is painfully non-trivial.
2. Displaying the key pair offers better support for devices that don't support downloads (e.g. many touch devices).