Virlutils

This release adds support for plugins to drive custom commands, viewers, and generators.

This release finally pushes virlutils over 70% test coverage! 🎉 Other changes are:

* Add license metadata (111)
* Normalize some strings
* Make nested commands easily patchable for testing

This release fixes a bug where license registration was broken due to a typo.

* Python 3.5 is once again supported since virl2_client supports it
* A `--no-start` flag has been added to `cml up` so one can import a lab but not start it right away
* Finally started adding unit tests for the new CML v2.x code!
* `cml down` will no longer clear the current lab
* All `cml up` to override the current lab when explicit lab-name or id arguments are given
* Support for multi-user lab ownership (when running as an admin user)
* Licensing is now done through the virl2_client library
* Licensed features can now be controlled with virlutils
* Config extraction has now been parallelized to increase performance
* Fix node existence checks
* Fix runtime on Windows when .virlrc is in the root of a drive
* Support for newer versions of Cisco NSO has been added

bugfixes / minor features

Many new enhancements in this release

* Detect use of management proxy server in topology, and use for ssh/telnet connections 28
* Add ability for `virl up` to block until nodes are online 39
* Added `virl id` to quickly return the sim id, which is useful for chaining commands e.g`virl use $(virl id)`
* Add ability to launch visualizations, UWM 29
* Ability to serve swagger-ui for the current VIRL server `virl swagger start` 29
* Improved error handling
* Bugfixes
* Increased test coverage