- attempting to make pom.xml files be compatible with Scala IDE

Fixed LBCORE-199 by adding a timestamp to the entry found in the zip file. This was suggested by Benoit Xhenseval.

ATTENTION, breaking change:
- removed NA_STRING_ARRAY because the content could
have been changed by other classes, previously.
- EMPTY is no longer public but private instead.

- avoid clearing the old map reference which may be still referenced elsewhere