Add support for range requests

[Kaliumhexacyanoferrat]

As the developer of a web application, I would like my clients to be able to request ranges, so that range-dependent functionality (e.g. resumption of downloads) can be provided.

Example

var download = Download.FromFile("./large.dat")
                       .Add(RangeSupport.Create()); // or convenience: .AddRangeSupport()

Host.Create()
    .Handler(download)
    .Run();

Acceptance criteria

• The requested range can be fetched as a typed and parsed instance from the IRequest
• The range support is implemented in a new concern placed in the IO module
• The implementation sends a Accept-Ranges: bytes header to indicate support on GET and HEAD requests (e.g. for download managers)
• The implementation returns a 200 and the original response if the content returned by the handler cannot be ranged/seeked
• The implementation returns a 416 if the range cannot be satisfied
• The implementation returns a 206 if the range can be satisfied
• The implementation does not support multiple ranges
• Range support is enabled for GET requests only
• The concern analyzes the request whether a range is requested and replaced the content returned by the server with a ranged content if so
• There are at least acceptance tests for all of the scenarios described above