Jupyter Enterprise Gateway 2.2.0rc1

This release of Jupyter Enterprise Gateway contains some significant improvements.

• Kernel management is now asynchronous, leveraging changes in the Notebook and jupyter_client packages. This allows for simultaneous kernel start requests, whereas these were sequenced previously.
• Kernelspec retrievals now will honor authorization lists to filter out unauthorized users. Previously, kernelspecs were not filtered so users would find that they're not authorized to use a given kernel until attempting to use it. Now, such users won't have that kernel in their available list.
• RemoteKernelManager has been refactored such that it can be used by applications directly - bypassing the need to stand up an EG instance.
• Various bug fixes.

NOTE: After producing the release, the commits were pushed too soon and we found an issue with the Spark-related images on Kubernetes (sigh). We will focus on getting those working ASAP and produce rc2 at that time. Sorry for the inconvenience.

Many thanks to the following contributors:

• @aviadr
• @golf-player
• Jalpan (@jalpan-randeri)
• Kevin Bates (@kevin-bates)
• Luciano Resende (@lresende)
• Luis Cabezon Manchado (@lucabem)
• Taeyeop Kim (@taeyeopkim1)