Make QnA Maker Active Learnings Thresholds user settable

[somigithub]

Issue: microsoft/botbuilder-dotnet#3706

C# Version PR: microsoft/botbuilder-dotnet#4383

This is the JS version for the same

[coveralls]

Pull Request Test Coverage Report for Build 154723

• 6 of 7 (85.71%) changed or added relevant lines in 2 files are covered.
• 9 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.07%) to 82.847%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
libraries/botbuilder-ai/src/qnaMakerDialog.ts	1	2	50.0%

Files with Coverage Reduction	New Missed Lines	%
libraries/botframework-streaming/src/webSocket/webSocketTransport.ts	2	80.65%
libraries/botframework-streaming/src/webSocket/webSocketServer.ts	7	66.67%

Totals
Change from base Build 154714:	-0.07%
Covered Lines:	14826
Relevant Lines:	17010

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💛 - Coveralls