Added everything to our high-level API that should be needed for WebSocket JSR.

* Add support for async send timeout as we need it for WebSocket JSR
* Allow to either run the FrameHandler in the io-thread or the XnioWorker
* Add support for fragmented WebSocket frames in the low-level api and make use of it in the high-level one
* Handle correctly traffic after close frame was received
* Detect if blocking operation is used but run in IO-Thread
Add concept of a Sender, to allow for traditional callback based coding
Change test to use sender
Add beginning of Undertow server builder API to make it easier to configure undertow.

Also add examples directoy, with some simple examples
Minor changes to the Undertow API
Change the way form redirect is handled
Add initial support for setting up security via the Undertow API
Remove BufferTransfer class, as it has been replaced by the Sender API
Add missing resumeWrites call