Pass ProtocolInfo to Init

To allow servers to handle protocol changes.

Add an optional Init func to the server, fix a data race

That takes a config struct from the client.

The old way of configuring the server was to pass env vars (which still works), but this was at best very cumbersome.

This also fixes a data race when both sending raw (e.g. log messages) and other responses.

Closes #10

Fix data race in client Close

Message streaming, ETag support etc.

The old request/response setup worked great, but had its limitations.

The new model types are request, message (zero or more) and a receipt.

The receipt can immplement some optional interfaces that gets/sets

* ETag
* ELastModified
* ESize

These may autimatically be set by the library if not provided by user (the `Etag` bassed on all message bodies if there's a hash function configured).

The primary use case for the above would be client side caching.

This also removes the slow Gob codec.

Fix Header.Status

The size indices were not adjusted when we changed to int16 recently, which made it
overwrite the header status. Which shows the importance of good tests.

Make Header.Version/Status uint16

One byte is a little on the small side, better changing this now before people start using this.

Fix error handling when server fails to start

Also make the ClientRaw.Close method more robust.

Fix data race in tailBuffer

Improve error handling when resolving codec

And remove the go.work files that masked a faulty test setup.

This is replaced with replace statements in the examples, which is OK as those are only used in
tests/as examples.

Give codecs a name

And pass that name to the server to be used if codec is not set.

This makes the simple cases more robust and smaller.