Replace axuno/TextTemplating with Razor.Templating.Core

[imprima]

Now, that we can Render Razor components outside of ASP.NET Core, it would be nice to replace
Axuno.TextTemplating with Razor.Templating.Core? See the description here. A big benefit was, that the razor views can be debugged out-of-the-box. A little downside is, that eventually a new project with type <Project Sdk="Microsoft.NET.Sdk.Razor"> is necessary for templating.