RFR [9] 8166568 & 8169492 jmod extract and bug fix

[Chris Hegarty]

This change adds a basic option to the jmod tool to extract all its contents to
the current working directory, 8166568 [1]. Additionally, there is a bug fix for
a public mutable static, 8169492 [2].

http://cr.openjdk.java.net/~chegar/8166568_8169492.00/

-Chris.

[1] https://bugs.openjdk.java.net/browse/JDK-8166568
[2] https://bugs.openjdk.java.net/browse/JDK-8169492