Use .ensime config to launch ENSIME server

[Alexey Alekhin]

Current state: #3 (comment).

See discussion on Gitter:

we used to use coursier in the clients, it was messy and lead to a lot of issues. Since we are already parsing the .ensime in the clients for the source directories, it was better to read the classpath from there.

@laughedelic why can't you just use the code that @vovapolu has written, and which the ensime community has paid for, to parse the .ensime file and launch the server the way everybody expects and agrees with the sbt-ensime setup.

So once the reusable part of the https://github.com/ensime/ensime-lsp-clients projects matures enough and is published, I'm going to use it to launch ENSIME server "the way everybody expects" 👌

The relevant piece of code: javaArgs.