Inter-isolate messaging

• Adds ApplicationMessageHub to send cross-isolate messages.

v2.2.1: Default charsets

• Allow HTTPCodecRepository.add to use specify default charset for Content-Type if a request does not specify one.

v2.2.0: Body codecs, body streams and files

• The default template created by aqueduct create is now mostly empty. Available templates can be listed with aqueduct create list-templates and selected with the command-line option --template.
• Bug fixes where aqueduct auth would fail to insert new Client IDs.
• joinMany and joinOne are deprecated, use join(set:) and join(object:) instead.
• HTTPCodecRepository replaces Response.addEncoder and HTTPBody.addDecoder.
• Streams may now be Response bodies.
• Request bodies may be bound in HTTPController with HTTPBody metadata.
• Adds file serving with HTTPFileController.
• Adds HTTPCachePolicy to control cache headers for a Response.
• Request.body has significantly improved behavior and has been optimized.
• Content-Length is included instead of Transfer-Encoding: chunked when the size of the response body can be determined efficiently.

v2.1.1: Adds ResourceRegistry (#248)

• Adds ResourceRegistry: tracks port-consuming resources like database connections to ensure they are closed when an application shuts down during testing.

v2.1.0

• Fixes race condition when stopping an application during test execution
• Adds validation behavior to ManagedObjects using Validate, ManagedValidator and ManagedObject.validate.
• ManagedObjects now have callbacks willUpdate and willInsert to modify their values before updating and inserting.
• Fixes issue with aqueduct serve on Windows.