ClassAnalyzer -depconfig option

[Mandy Chung]

Alan,

I modify the dependencies output to indicate if a class is marked as an 
optional dependency.

Webrev at:
   http://cr.openjdk.java.net/~mchung/jigsaw/tools/webrev.01/

make/config/jdk7.depconfig is the current list of dependencies that are 
from Class.forName or service provider.  You can add additional 
dependencies to this list.  You can also specify optional dependencies.  
For example, you can add
 
@Optional java.io.File -> java.nio.file.Path

It specifies that java.nio.file.Path referenced from java.io.File is an 
optional dependency.

Can you review this change?

Thanks
Mandy