/api/table/country sometimes outputted '-0' instead of '0'
Single filter were loaded from URL as multiple filters #3039

This lead to confusion on /contribute/jmp leading to several
duplicated or meaningless HTTP request. And also firing up to 3
times the gims-tablefilter-computed event for no reason.
Filter can have several parents
Qatar and Trinidad and Tobago have only data for total
Merge branch 'develop'