Add support for Index and Range types, C# `..` operator

[Jand42]

Tests already exist (but marked to skip): https://github.com/dotnet-websharper/core/blob/1593e1045e49ae23836e3573659a551718deb8ef/tests/WebSharper.CSharp.Tests/Syntax.cs#L690-L708

• [ ] Add proxies for the structs
• [ ] Add support for C# ^ (index from end) and .. (range) operator syntax
• [ ] Add support for obj[...] index of common collection types using Index/Range