Moving src.zip out of the lib directory of the JavaFX SDK

[Kevin Rushforth]

We deliver a set of modular jars in the lib directory of the standalone 
JavaFX SDK. We also deliver src.zip for use by IDEs into that same 
directory. If you add the lib directory to your application's module 
path in your IDE, it will try to load src.zip as if it were a jar file, 
and will fail. This is a pain point for developers using the SDK. This 
problem has been raised on the mailing list a couple of times, and I 
think it's time to fix it. This issue is tracked in JBS by JDK-8258499 [1].

I propose to move the src.zip file from the lib directory to the top 
directory of the SDK.

Alternatively, we could create a new directory for src.zip (either a 
sibling of lib or sub-directory under lib). However, I think it would be 
easier to find in the top dir of the SDK, and I don't see the need for a 
new directory just to hold src.zip.

Before I create the PR and the associated CSR, I'd like to hear 
developer's opinions on this.

-- Kevin

[1] https://bugs.openjdk.java.net/browse/JDK-8258499