SeriesInfoExtractorService: introduce a method for parsing only sales-related info

The puzzle `995-a90e239c` from #995 has to be resolved: 

https://github.com/php-coder/mystamps/blob/bc3fe55ea8748c0231f45e6f403419e6b0a02df8/src/main/java/ru/mystamps/web/feature/series/importing/sale/SeriesSalesImportServiceImpl.java#L82-L82

The puzzle was created by Slava Semushin on 03-Jun-19
