Improve MultiSocket::ssl_handle
Beast improvements and vflib compatibility module work

* Add CallQueue vflib compatibility class
* Use run instead of run_one
* Merge BindableServiceQueue into CallQueue
* Take BEAST_VARIADIC_MAX into account
* Fix license headers as suggested by Vinnie
* Remove obsolete comment
* Add ManualServiceQueue
* Add ManualServiceQueue to beast_vflib include
* Move static unit test variables of header only classes to module cpp
* Remove no longer used mutex member
* _VARIADIC_MAX maxes out at 10
* Correctly apply BEAST_VARIADIC_MAX
* Merge BindableServiceQueue into CallQueue
* New GuiServiceQueue and its JUCE dependency
* Fix leftover merge errors
* Fix CallQueue unit test
* Don't use bassert for better CI support