refactor ES test setup once again, making the process global
so it can be used in multiple test classes - and added reset/cleanup per test
really isolate the ES test process, and manage it all in a temp directory
beware: ugly code - first working version ;)
don't use 9299 as random port, or the transport port would be 9300
(and potentially conflict with a default system ES install)
add some comments explaining the steps in the ESProcess setup