Botkit: Port the Facebook connector to the new format used by Botkit #next

[benbrown]

[benbrown]

When we undertake this, we should make sure we can support much requested feature of multi-tenancy.

I propose we do this using the model I applied to the new slack adapter, that is, developers who want to use multi-tenancy must provide a mechanism for providing the appropriate API credentials based on a field in the incoming message.

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[benbrown]

This is done! OMG! MULTI-PAGE SUPPORT!!!

https://github.com/howdyai/botkit/tree/next/packages/botbuilder-adapter-facebook