data: Add ability for `IPaginationSource`s to specify how to get settings. The `IPaginationSource` has a new `getSettingAccessor` method that returns how to access settings values on items in the pagination source. A default accessor is also available, which uses standard attribute lookup. Also clean some stuff in `LazyPageConfigData`.

#!/bin/sh

CUR_DIR="$( cd "$( dirname "$0" )" && pwd )"
CHEF=${CUR_DIR}/../bin/chef
OUT_DIR=${CUR_DIR}/../piecrust/resources/messages
ROOT_DIR=${CUR_DIR}/messages

$CHEF --root=$ROOT_DIR bake -o $OUT_DIR
rm ${OUT_DIR}/index.html