Changes:
* Fix broken tests and VS solutions caused by source code reorganization
* Add a check to validate generated code and solutions on PRs
* backport some source code reorg to src/Identity
* Fix startvs.cmd if you've already run build.ps1
* Add PR checks for tests on Linux/macOS
* Skip broken Nginx tests
* Add conditions to skip IIS tests on non-Windows platforms
Changes:
* Condense Routing.sln into HttpAbstractions.sln
* Workaround NU1105 by adding all ProjectReferences to the .sln
* Workaround exceptions in the ReferencesHostBridge by moving Reference items to a temporary item group
* Add a 'startvs.cmd' script for launching VS with the right env variables
* Remove RangeHelper test project
* Move RangeHelper tests into StaticFiles.Tests and add target for NPM restore
Nate McMaster