RFR: 8223955: Eliminate or reduce mixing of old File API and new Path/Files APIs

[alexander . matveev]

Please review the jpackage fix for bug [1] at [2].

Substituted old File APIs with Path/Files APIs when it was possible and 
makes sense.

[1] https://bugs.openjdk.java.net/browse/JDK-8223955
[2] http://cr.openjdk.java.net/~almatvee/8223955/webrev.00/

Thanks,
Alexander