8168789: ModuleReader.list and ModuleFinder.of update

[Alan Bateman]

We have a lot changes in the jake forest. I need to bring some of the 
changes that aren't tied to JSR issues into jdk9/dev to unblock others.

Specifically, I'd like to bring over the changes that are needed to 
allow jlink to support linking of MR JARs. Steve has initial patches 
(there's a separate thread reviewing that) but it needs more further 
work in jlink for it to detect the version of java.base that it is 
linking into the target runtime. That work will not merge if done in 
jdk9/dev without some of the changes from jake.

I also want to bring over the changes to the derivation of the module 
descriptor for automatic modules as jake has several fixes that aren't 
in JDK 9.

In addition we have a new list method on ModuleReader in jake that 
people working on tests for JDK 9 need in the main line. I'd like to 
bring over the current implementation (we can iterate on it further in 
jake if needed).

The webrev with the changes that I'd like to bring over is:
     http://cr.openjdk.java.net/~alanb/8168789/webrev/

There are other changes to many of the same files in jake that I'm not 
proposing to bring over at this. I've tried to keep it so that the 
merging when sync'ing up jake won't be too difficult.

-Alan.