ZA: Fix the organisation party sub-page display of people
ZA: Fix the organisation party sub-page display of people

Previously this produced buggy and confusing results due to, for
example, not taking to account that people might change party between
terms of office, and various other complications.

Fixes #1450

mysociety/pombola,hzj123/56th,ken-muturi/pombola,mysociety/pombola,hzj123/56th,patricmutwiri/pombola,mysociety/pombola,geoffkilpin/pombola,ken-muturi/pombola,patricmutwiri/pombola,patricmutwiri/pombola,hzj123/56th,ken-muturi/pombola,patricmutwiri/pombola,geoffkilpin/pombola,patricmutwiri/pombola,geoffkilpin/pombola,patricmutwiri/pombola,hzj123/56th,ken-muturi/pombola,geoffkilpin/pombola,hzj123/56th,mysociety/pombola,geoffkilpin/pombola,geoffkilpin/pombola,mysociety/pombola,ken-muturi/pombola,mysociety/pombola,hzj123/56th,ken-muturi/pombola