implement () -> () as Runnable downcalls and upcalls

[ktoso]

resolves #99

Now we're able to

        CountDownLatch countDownLatch = new CountDownLatch(3);

        ExampleSwiftLibrary.globalCallMeRunnable(new Runnable() {
            @Override
            public void run() {
                countDownLatch.countDown();
            }
        });
        assertEquals(2, countDownLatch.getCount());

        ExampleSwiftLibrary.globalCallMeRunnable(() -> countDownLatch.countDown());
        assertEquals(1, countDownLatch.getCount());

        ExampleSwiftLibrary.globalCallMeRunnable(countDownLatch::countDown);
        assertEquals(0, countDownLatch.getCount());

when given a

public func globalCallMeRunnable(run: () -> ())

[ktoso]

We can make this more reusable and take the name from self but let's do that later