[maven-release-plugin] prepare release 2.8.0-beta1
[maven-release-plugin] prepare for next development iteration
COMETD-499 (JQuery bindings use the "jQuery" object too early).

Removed early references to the jQuery object.
Added automatic license header check also to JavaScript files.
Split WebSocketTransport into a Jetty-independent base class that
other can extend to implement the transport in other containers.
Merged branch '2.8.x' into 'master'.