RFR 8171138: Remove FileCopierPlugin

[Sundararajan Athijegannathan]

Please review http://cr.openjdk.java.net/~sundar/8171138/webrev.00/ for 
https://bugs.openjdk.java.net/browse/JDK-8171138

Piggybacking cleanup: release file generation ("TOP" entry type 
handling) moved to accept(ResourcePoolEntry)

Thanks,
-Sundar