Change headings and titles to use sentence-style capitalization

[mairaw]

Microsoft's guidance for titles and headings is to use sentence-style capitalization. So I'm adding this information to our template file but also we need to review existing topics to have the proper capitalization.

[richlander]

This topic and the ones around it are good ones to start with.

https://docs.microsoft.com/en-us/dotnet/articles/core/tools/dotnet-test