nfs: ExportFile returns Iterable instead of Collection

best practice.

Acked-By: Paul Millar
pom: java7 is allowed

Acked-By: Paul Millar
src: towards java7: use diamond operator

Acked-By: Paul Millar
src: towards java7: use try-with-resources

Acked-By: Paul Millar
src: towards java7: use muticatch

Acked-By: Paul Millar