New rules and group to get numebr of stories from mulitple sources

The number of stories information for HEI/HEB attributes are retrieving from multiple sources, the original rule HeightandFloorspaceRule is too big now after merging the height and stories information together. So the conclusion is to implement the new StoriesGroup and its rules, the rules are splitted by the sources, such as OSM stories rule, GHSL stories rule. The decider is the StoriesRule which decides the priorities of the sources, if new sources are added, the users should modify the decider for the priorties and add new rules for the new sources.