Reworked legacy routing to allow invocation from any dir

Example runs:
pushd $VUFIND_HOME
php util/ping.php                           # SIMPLEST CASE
cd import
php .././util/./ping.php                    # HANDLE MISDIRECTION
cd ../util/
php ping.php                                # LEGACY CASE
php ./ping.php                              # LEGACY (equivalent)
php ../util/ping.php                        # HANDLE MISDIRECTION
php ../util/./ping.php                      # HANDLE MISDIRECTION
cd
php /full/path/to/vufind/util/ping.php      # FULL PATH TEST
ln -s /full/path/to/vufind ./myvufind       # BEGIN SYMLINK TESTS
php myvufind/util/ping.php
php ./myvufind/util/ping.php
popd