Remove obsolete nuget T4MultiFile

It's from back when we were using T4 templates
Visual Studio cleanup of project files and nugets
Set assembly versions back to 1.0.0

These are supposed to be changed as part of build process on build
server.
Reorganize build process

* Use Artifacts folder as build output, ignored from repo
* Use msbuild files to define paths to src and test projects
* Add batch files for building, testing, nuget and zipping
* Add NUnit and 7Zip tools to be able to build and test locally