data: Fix problems with using non-existing metadata on a linked page. The page data wrapper now has supports for loader to raise a custom exception to declare that they can't return a value after all (this is especially useful for the wildcard loader). The returned value, if any, is also now cached properly.

#!/bin/sh

CHEF_DIR=`dirname $0`
if `hash readlink 2>&-`; then
    LINKED_EXE=`readlink $0`
    if [ -n "$LINKED_EXE" ]; then
        CHEF_DIR=`dirname $LINKED_EXE`
    fi
fi
python $CHEF_DIR/../chef.py $@