New Paginators class to manage the creation of all Paginator instances

- GenericPaginators use a String[] instead of an enum for "where" values.
  GenericPaginator.getWhereValues() replaces this.
- Concrete GenericPaginator classes have package-protected constructors
- GenericPaginator.getAsString(Where) has been removed
- All Where classes were removed (except for ModeratorPaginator.Where)