Channelstream

Changed
* Logout and api-explorer links in admin panel
* Persist auth cookie for admin panel

Added
* `channelstream_utils` command, right now it can create fresh config INI files
Removed
* [breaking] dropped six compat layer
* [breaking] test only in python 3.6+
* [breaking] Allow configuration only from ini files, drop all other arguments from CLI
Changed
* Admin views can also be accessed when authenticating via API keys
* Updated frontend code to support ESM browsers by default, fallback to ES5 browsers optionally
* Depend on pyramid_apispec 0.3.3
* /api-explorer is now only accessible for admin users

Changed
* Pinned Marshmallow version to <3.0.0
* Bumped pyramid_apispec

Changed
* AuthTkt instead of basic auth, introduces optional `cookie_secret`
* Used lit-element 2.0.1 for components
Fixed
* changed garbage collection and hearbeat handling that should end with smaller callstacks
* fixed a heartbeat check that could result in greenlets run forever

Added
* `enforce_https` config option forces the servers to reject non-ssl requests
* `http_scheme` config option can be used to enforce HTTPS urls if proper proxy headers are missing
* `/admin/debug` route for printing out greenlets
Removed
* JS Client code was moved to npm and separate repository
Changed
* Moved to lit-element 2.0.0rc5

Changed
* Depends on pyramid_apispec==0.3.1