Add services to support additional bot framework channels

[tonysurma]

(originally created by @toolboc)

Out of the box, the Microsoft bot framework supports integration with Facebook, Skype, Microsoft Teams, GroupMe, Slack, and Twilio to name a few.

It may be advantageous to allow users to easily leverage this project in the various support channels to increase coverage for users. Certain channels offer different features than others and it may be useful to add channel specific logic to handle those feature, for example call hand-off within Skype.

For information on configuration of Bot Framework supported channels, see:
https://docs.microsoft.com/en-us/bot-framework/bot-service-manage-channels