Embryonic but functioning JSR223 support

[rjolly]

This is mainly to obtain feedback. Once on track, I will consider remaining features like compiled scripts, variable bindings, classpath issues and so on, to be on par with the 2.12 implementation.

How to run:

jrunscript -J-Djava.class.path="C:\Program Files\Java\jdk1.8.0_191\lib\tools.jar;dotty-library_0.11-0.11.0-RC1.jar;scala-library-2.12.7.jar;scala-asm-6.0.0-scala-1.jar" -classpath dotty-compiler_2.12-0.12.0-bin-SNAPSHOT-nonbootstrapped.jar;dotty-interfaces-0.11.0-RC1.jar -l scala
scala> "hello world"
val res0: String = hello world

hello world
scala>

[dottybot]

Hello, and thank you for opening this PR! 🎉

All contributors have signed the CLA, thank you! ❤️

Have an awesome day! ☀️

[Blaisorblade]

This doesn’t look very invasive but it needs tests, unless there’s an extremely good reason.

[Blaisorblade]

@rjolly So, that looks cool!

As a follow-up: to also test what you asked, I asked @smarter. You can do that by creating an SBT project that depends on the compiler, and test it using sbt-scripted.
An existing such test is in sbt-dotty/sbt-test/sbt-dotty/compiler-plugin/ — see in particular sbt-dotty/sbt-test/sbt-dotty/compiler-plugin/build.sbt for our to load the compiler; commands to give to SBT appear in sbt-dotty/sbt-test/sbt-dotty/compiler-plugin/test.

[Blaisorblade]

@rjolly But I'd be already happy to merge this, honestly, if you can't get to that quickly. Let me know.

[rjolly]

@Blaisorblade The problem was with the classloader used by the new ScriptEngineManager() call. I fixed it. Then, by putting the test in run-with-compiler, everything works fine.
@smarter I removed the color. The best would be to switch off the output altogether but I do not know how to do that. I added some documentation.

[smarter]

LGTM, any more comments @allanrenucci ?