fixes #4075 - also will be able to store user's favourite filters on any screen implementing Listing.pm

git-svn-id: https://svn.eprints.org/eprints/trunk/system@7855 9491667e-5006-0410-a446-efbe8990b998
Update Listing.pm

Fixes https://github.com/eprints/eprints/issues/242
 * Fixed undef warning

git-svn-id: https://svn.eprints.org/eprints/trunk/system@7391 9491667e-5006-0410-a446-efbe8990b998
revert defining  - cherry-picked commit from master branch instead
 * Applied epscript fixes from Mark Gregson <mark.gregson@qut.edu.au>

git-svn-id: https://svn.eprints.org/eprints/trunk/system@7824 9491667e-5006-0410-a446-efbe8990b998