Review Request: 8178404: jlink --suggest-providers should list providers from observable modules

[Mandy Chung]

Webrev:
  http://cr.openjdk.java.net/~mchung/jdk9/webrevs/8178404/webrev.00/index.html

--suggest-providers should suggest providers from any observable modules
rather than the resolved modules.  This patch also improves the output and
fixes JDK-8178405 and JDK-8178327.  --add-modules has no effect to the
suggested providers when —suggest-providers is specified.

Mandy