Remove a bunch of unnecessary (and *theoretically* dangerous, in a very unlikely scenario involving custom cultures installed on a box) C# 7 string $"...{...}..." usages

Fixed some syntax errors in project.json files

Add InListStringSplitCount; when set, causes `in @foo` parameters to be implemented using string_split

Test for #524 (believed to be a failing test; cannot validate or fix until I get the latest tooling installed)

Note: build.sh needs love from OS X/*nix later to match

This fixes null refs with the DNX MSBuild targets when building from
Visual Studio.

Related issue: #520

RC2 Upgrade!

Tooling changes need to live in the repo now so the build doesn't FUBAR
every time we change the script.

Note: on a nuspec comparison, the following dependencies aren't there
anymore: Microsoft.CSharp, mscorlib, System, and System.Core aren't
explicitly specified in frameworkAssemblies anymore. The only one of
these I can imagine mattering is Microsoft.CSharp.

https://github.com/dotnet/corefx/issues/1612 is now closed, tests
working.