Drop remote debug tunnel support

[philwebb]

It's going to be hard to support JDK 9

[snicoll]

@philwebb I've started the work in 16fcbb7. I am not sure I cleaned it up properly but that can be a good base maybe?

[snicoll]

@philwebb ping? It would be nice to get that in M3 so that we can see ASAP if people are complaining.

[wilkinsona]

FWIW, it looks good to me @snicoll.