Fix Teams Handler for task/fetch and submit | TaskModule scenario

[daveta]

Fixes # #1212

Description

• Fixes Teams Handler for Invoke/task/fetch and Invoke/task/submit.
  • task/submit now returns TaskModuleResponseBase, which can be used to return type message or continue.
  • Following demonstrates returning a message which casts to base class.

    protected async onTeamsTaskModuleSubmit(context: TurnContext, taskModuleRequest: TaskModuleRequest): Promise<TaskModuleResponseBase | void> {
        var reply = MessageFactory.text("OnTeamsTaskModuleFetchAsync Value: " + JSON.stringify(taskModuleRequest));
        await context.sendActivity(reply);
        var response : TaskModuleMessageResponse = { type: "message", value: "Hello", };
        return <TaskModuleResponseBase> response ;
    }

• Scenario TaskModule, which demonstrates task fetch/submit.

[coveralls]

Pull Request Test Coverage Report for Build 81532

• 0 of 6 (0.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.04%) to 87.465%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
libraries/botbuilder/src/teamsActivityHandler.ts	0	6	0.0%

Totals
Change from base Build 81402:	-0.04%
Covered Lines:	4505
Relevant Lines:	4964

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💛 - Coveralls