Windows Templates and Pipeline Fixes

This PR starts to integrate the new content pipeline with the Windows VS templates.

 - Fixed up the templates to appear in VS with some reasonable order. (Fixes #3191)
 - Removed old .targets file and fixed up the new one.
 - Removed old Content VS template project.
 - Added support for new content pipeline to Windows template.
 - MGCB no longer shows usage on empty content builds.
 - Fixed Pipeline tool to use EXE path for loading item templates.
 - Fixed build script to delete old template .zip files before rebuilding them.

Is this for the case where the game project wasn't changed so the content is not built (was especially annoying if content build failed the last time)?