Import-Tool: Improvements and bugfixes

The patch contains some small fixes and a little cleanup for the import tool.

In details the following things are changed:

parent pom
Use the latest release of Hippo (7.7.5)
Use commons-io 2.2

RepositoryDocument / RepositoryFolder
Use FilenameUtils from commons-io for normalizing paths (Fixes a bug, where
sometimes a SLASH was missing in the path)

DocumentCreator:
For convenience always call doPostponedRefs after saving a created Document.
Replaced deprecated node.getUUID() with node.getIdentifier()
Changed some logging from warn to debug.
Fixed processSubProperties to pass the created Node(newNode) to
bean.beforePersisted instead of the parent node (Which was wrong, because the
calling bean is the bean of the newNode).