Orchestrator UX integration

[boydc2014]

1. Provide new choice in recognizer (orchestrator) with the designed tooltip and help link.

   • after user choose orchestrator the downloading will starting by default, before downloaded, the start bot is not allowed
   • before [Adaptive] Setting and managing recognizers for adaptive dialogs botbuilder-dotnet#4651 is addressed, after user choose orchestrator, we will have to user $designer.id to mark this is orchestrator instead of LUIS

2. Create a new filed in settings page for the base model selection (by default is the least layer bert-3layers)

3. Download the base model to a shared location. Consider both web scenario and electron scenario.

4. Generate the recognizer dialogs once user choose Orchestrator, related PR: Further revision to form element order #435

5. Do the orchestrator:build + luis:build based on the dialog choices (@lei9444)

6. Verify it works locally (at this time, remote deploy should not work, because base model missing in remote)

[luhan2017]

Will this impact the qna scenario? Based on my understanding, if use selects Orchestrator, it means he/she selects Ochestrator+QnA, and a CrossTrainedRecognizer will be generated?