8035782 : sun/launcher/LauncherHelper$FXHelper loaded unnecessarily

[Neil Toda]

Please review Launcher change and test.
I've added to the Launcher test : FXLauncherTest.java
The test will now check that LauncherHelper$FXHelper is not loaded for 
non-JavaFX class and jar files.

webrev.02 contains only review suggestions from webrev.01 and the new 
test class.

http://cr.openjdk.java.net/~ntoda/8035782/webrev.02/

for bug:

https://bugs.openjdk.java.net/browse/JDK-8035782

Thanks

-neil