Add to collection: stamps quantity should be specified by default

[0pdd]

The puzzle 477-128af1e6 from #477 has to be resolved:

mystamps/src/main/java/ru/mystamps/web/controller/dto/AddToCollectionForm.java

Line 31 in 4cb3692

// @todo #477 Add to collection: series quantity should be specified by default

The puzzle was created by Slava Semushin on 13-Jun-18.