[PORT] Make the CRUD of the template consistent

[tomlm]

Port this change from botbuilder-dotnet/master branch:
microsoft/botbuilder-dotnet#3622

Originally, we treat LG file as the combination of templates and use empty string as the separator.
From now on separator "\r\n" would be used.

So, if we update a template with the body "- A", we would always get the body "- A" but not "-A\r\n" in any case. This idempotent relationship will greatly increase robustness and consistency

Changed projects

• Microsoft.Bot.Builder.LanguageGeneration
• Microsoft.Bot.Builder.LanguageGeneration.Tests