Jupyter Enterprise Gateway 0.8.0 release

Jupyter Enterprise Gateway release v0.8.0 focuses on security-related updates and includes the following:

• Add initial authorization and impersonation support (#235)
• Add JupyterLab option to elyra/nb2kg image. (#237)
• Connection info not returned from launchers in Python 3 (#241)
• Add proxy configuration to kernelspec (#240)
• Integration test enhancement (#245)
• First version implementation of impersonation integration test (#246)
• Fix R-kernel to show kernel ID as app name in YARN RM (#248)
• Fix SSH tunnel termination on kernel shutdown (#244)
• Validate cell execution results immediately after execution (#249)
• Fix signal_kernel() to nolonger assume its only used for interrupts (#252)
• Update NB2KG references to reflect recent repo move and release. (#255)
• Apply recent Toree kernel command-line additions to scala sample configurations (#231)
• Updated YARN cluster mode kernelspecs to use new spark conf parameter (#256)
• Encrypt handshake between the Kernel Launchers and the EG (#266)
• Initial changes of itests to use pytest (#268)
• Add support for kernel interrupts for R kernels (#269)
• Use UTF-8 encoding while encrypting and decrypting (#273)
• Limit the dependency on Tornado to versions less than 5.0 (#276)
• Update troubleshooting guide for pycrypto install (#275)
• Add a trouble shooting section for Kerberos authentication (#284)
• Add support for specifying port range to use for kernel and EG ports (#270)

Thanks to the following contributors:

• Alex Bozarth (ajbozarth)
• Alan Chin (akchinSTC)
• Charlie Yang (charlieeeeeee)
• Kevin Bates (kevin-bates)
• Kun Liu (liukun1016)
• Luciano Resende (lresende)
• Sanjay Saxena (sanjay-saxena)

See the v0.8 milestone on GitHub for a complete list of pull requests involved in this release.