link suggestions together so that combinations appear more prominently

[LucaBernstein]

thought at first about taking note of what was before a suggestion entry last.

second thought was: add a suggestionRelation table that notes per user, previous entry type, next entry type the last value used and suggest it at top. for that check, that entry types are well defined (leading to #157): make definitions more lose and less hard-coded.

should be scenario and unit tested.