RFR: JDK-8006884(2nd round): (fs) Add Files.list, lines and find

[Henry Jen]

Hi,

Updated based on feedback,

http://cr.openjdk.java.net/~henryjen/ccc/8006884.1/webrev/
http://cr.openjdk.java.net/~henryjen/ccc/8006884.1/specdiff/

Changed from previous request,

1. DirectoryStream.entries() is renamed to DirectoryStream.stream().
2. Clarify operating closed stream returned from Files.list as
end-of-stream, from Files.walk will throw IllegalStateException, and
added test case.

Cheers,
Henry