Review Request JDK-8169925: Organize licenses by module in source, JMOD file, and run-time image

[Mandy Chung]

This proposes to organize license files by module in source, JMOD, 
and run-time image.

A summary of the proposal:
1. Organize third party notices by module in the source as follows:
    src/$MODULE/{share,$OS}/legal/*
 
The `legal` directory contains one file for each third party
library in the module, for example,
    src/java.base/share/legal/asm.md
                              unicode.md
                              zlib.md

The proposed template for this file is described in [1] and JEP 201 
will be updated to reflect this proposed source layout.

2. Introduce a new LEGAL_NOTICES section in JMOD format. A new jmod
   option `—-legal-notices` is added to package legal notices in
   a JMOD file.

3. At jlink time, jlink will copy all legal notices from JMOD files
   to the `legal` directory in the run-time image.  A plugin is
   added to de-duplicate the legal notices if the filename and the
   content matches that may reduce the image footprint.

4. THIRD_PARTY_README in the top-level directory of each repo is removed.
   Manual edit to this file, multiple copies is no longer needed.

Webrev at:
   http://cr.openjdk.java.net/~mchung/jdk9/webrevs/8169925/webrev.00/

Mandy
[1] https://bugs.openjdk.java.net/browse/JDK-8169925