Session support

This update changes how to use DiSL. It's no longer needed (its even useless) to specify the instrumentation jar file in DiSL server JVM classpath. From now on, the instrumentation jar is passed as an argument to the dislagent --agentpath option and is sent to the server on client initialization phase.

This required to change communication protocol between DiSL Server and DiSL agent (#1 (closed)) as well as refactoring the main DiSL instrumentation library, mainly to use the session specific classloader and therefore to be less static.

As a part of this update, the project directory structure was updated (discused in #5 ) to reduce the number of packages and flatten the public API of the instrumentation library. Also DiSL server was extracted to its own subpackage with its own build.xml file.

Both examples and tests were adapted to the new workflow, thus the state of the repository should be consistent.

Please make a code review, and let me know if I forgot something.