Debug mode

[martin-azpillaga]

These changes enable attaching a debugger to a running language server.
First, update the plugin version and choose a port for the language server to listen for debuggers:

Next, create a Remote JVM Debug task in idea pointing to the same port:

Start the editor as usual. While the editor is running, run the idea task to attach the debugger to the running language server. Now the code will stop in the breakpoints located in the language server's code:

To debug initialization code, set the suspendExecutionUntilDebuggerAttached flag to true:

The language server won't start until the debugger task is launched, and you can inspect the initial messages:

[alessiostalla]

The code looks good and the feature is really useful, I would just update the readme

[martin-azpillaga]

Thanks @alessiostalla for the comments. I have pushed new commits that address the main issues.