SeriesService.countSeriesOf(): move to CollectionService

[0pdd]

The puzzle 927-e88d3d70 from #927 has to be resolved:

mystamps/src/main/java/ru/mystamps/web/service/SeriesService.java

Line 38 in ba083d8

// @todo #927 SeriesService.countSeriesOf(): move to CollectionService

The puzzle was created by Slava Semushin on 24-Jul-18.