Clarify usage of word "filter" in descriptions

The verb "filter" is used profusely in descriptions (there's 29 occurrences, for example `spec/parameters/query/transferMosaicId.yml`) and it can be understood as both "filter-in" (include) or "filter-out" (exclude).
The meaning is probably clear to all our devs (and maybe all REST devs out there) but it won't hurt to be more specific.