Update to Buildtools 2.0, Remove remaining project.json's (dotnet/core-setup#2373)

Update to Buildtools 2.0, Remove remaining project.json's (dotnet/core-setup#2373)

* Exclusively use the 2.0 CLI and 2.0 buildtools.

* Fix Linux problems.

* Don't run chmod on Windows.

* Make sure DOTNET_SKIP_FIRST_TIME_EXPERIENCE is set in init-tools.

* Clean up some MSBuild properties

* Auto-update WCF dependencies

* Delete root-level global.json

* Change how dependency versions are specified.

Use full versions rather than concatenated strings.

* Use "azureedge" download URL in init-tools

* Use TargetFramework=netstandard1.0 instead of dnxcore50 in deps.csproj

* Link CoreFxVersion to Microsoft.Private.CoreFx.NETCoreApp

* Use "DotnetRestoreCommand" instead of "DnuRestoreCommand" in properties.

* Check RunningOnUnix in dir.props (recommended pattern)

* Change an additional use of DnuSourceList to DotnetSourceList

Commit migrated from https://github.com/dotnet/core-setup/commit/50d699be379ae5c85a55efe7b8c3a763f5822e26