Improve paging in c8y API

When implementing data grid with paging to show items fetched using the c8y API the implemented paging is not working very well. In our case we need to get the total count of items (with query params: withTotalPages=true, pageSize=1), the filtered count of items (with query params: withTotalPages=true, pageSize=1, filter query) and the data page it self. Three requests are required to fetch this information. It would be easier if the PagingStatistics would include the total items count and not the count of pages. The count of pages we can calculate by ourself when we need that information. Then we could fetch the required information with two requests (or only one when no filter is applied).