GraphManager/Engine Headers + minor WebSocket cleanup

[designatednerd]

In this PR:

• Added default and ability to set non-default name and version headers for Apollo GraphManager and Apollo Engine
• Pulled some web socket components out of the giant class file into their own classes, start adding inline documentation (to the extent that I understand what's happening 🙃).
• Added a convenience extension for getting stuff out of a bundle's info dictionary.

[js]

I actually decided against this on my end as I'm increasing the build number on each build (based of number of commits) and it makes the "Clients" view in Apollo Engine a bit noisy for the non-public environments/variants. YMMV of course and it's always configurable anyway.

[designatednerd]

Yeah in my past experience when I've had build number auto-incrementing it's actually been quite helpful in being able to identify exactly where I broke something 😄. And as you said, it's configurable, so if people don't like the default, they can always adjust.