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.