Update schema to include strings for unions and other minor fixes

[chrimc62]

This makes it so that sdk.schema properly validates again and was generated by updated bf dialog:merge.

[fuselabs]

✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.AI.Luis.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.AI.QnA.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.ApplicationInsights.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.Azure.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.Dialogs.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.Integration.ApplicationInsights.Core.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.Integration.AspNet.Core.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.TemplateManager.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.Testing.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Configuration.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Connector.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Schema.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Streaming.dll compared against version 4.6.3

[coveralls]

Pull Request Test Coverage Report for Build 103701

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 1282 unchanged lines in 160 files lost coverage.
• Overall coverage decreased (-1.5%) to 78.039%

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Files with Coverage Reduction	New Missed Lines	%
/libraries/Adapters/Microsoft.Bot.Builder.Adapters.Facebook/FacebookAdapterOptions.cs	1	86.67%
/libraries/integration/Microsoft.Bot.Builder.Integration.ApplicationInsights.Core/ApplicationBuilderExtensions.cs	1	71.43%
/libraries/Microsoft.Bot.Builder.AI.LUIS/LuisApplication.cs	1	96.36%
/libraries/Microsoft.Bot.Builder.AI.LUIS/V3/LuisApplication.cs	1	96.43%
/libraries/Microsoft.Bot.Builder.AI.LUIS/V3/LuisUtil.cs	1	96.35%
/libraries/Microsoft.Bot.Builder/BotStateSet.cs	1	85.0%
/libraries/Microsoft.Bot.Builder.Dialogs/Debugging/DebugSupport.cs	1	75.0%
/libraries/Microsoft.Bot.Builder.Dialogs/Debugging/SourceRange.cs	1	46.15%
/libraries/Microsoft.Bot.Builder.Dialogs.Declarative/ComponentRegistration.cs	1	71.43%
/libraries/Microsoft.Bot.Builder.Dialogs.Declarative/Resources/ResourceExplorer.cs	1	96.3%

Totals
Change from base Build 103515:	-1.5%
Covered Lines:	21179
Relevant Lines:	27139

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💛 - Coveralls

[tomlm]