Full implementation of ActivityHandler and MVC integration DCR

[johnataylor]

• full implementation of integration for Asp Net both Core and WebApi
• implementation of ActivityHandler and strongly typed ITurnContext
• unit tests for ActivityHandler

TODO:

• unit tests for integration components
• potentially more logic in ActivityHandler, depends on what @Stevenic comes up with
• decide on names (so far I've left the working "Ex" naming but we know we don't want to keep that)
• update TestBots in the solution to use integration components (this can be a follow on check in)

[coveralls]

Pull Request Test Coverage Report for Build 48714

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 68 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+3.6%) to 73.038%

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Files with Coverage Reduction	New Missed Lines	%
/libraries/Microsoft.Bot.Builder.Dialogs/Choices/ChoiceFactory.cs	7	79.7%
/libraries/integration/Microsoft.Bot.Builder.Integration.AspNet.Core/BotMessageHandler.cs	7	0.0%
/libraries/Microsoft.Bot.Builder/Adapters/TestAdapter.cs	54	79.86%

Totals
Change from base Build 48458:	3.6%
Covered Lines:	3936
Relevant Lines:	5389

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💛 - Coveralls

[cleemullins]

Some Minor nits, but really, this is quite nice.

[drub0y]

Per comment below on the WebAPI implementation, I'm finding this "hoisting" of the BotAdapter class up to the integration layers very strange. I don't yet see the value in this particular change at all, but, as I say in the comment, maybe I need to see what you do in the actual integration layers now to tie it all together.

[johnataylor]

@cleemullins @sgellock @Stevenic with Ben's changes from today this should give us parity.