Review request: Install module content into zip files

[Mark Reinhold]

http://cr.openjdk.java.net/~mr/jigsaw/rev/zip-module-content/

This change causes a module's classes and resources to be stored in zip
files within the target library, regardless of whether the module came
from a .jmod file or from explicit class and resource trees.

This will help performance a tiny bit on some platforms and a small bit
on others.  It's also a prelude to an even more-efficient library format,
which will store zip-file offsets directly in module configuration files
so that we never have to read zip-file directories.

- Mark