Make two URLs for the two County Performance experiments

We don't want to risk people following links from the earlier trial
experiment while the larger experiment is running and the data being
contaminated by that. The safest way to do that is to use two different
base URLs for the two experiments - one is now /county-performance and
the other is /county-performance-2

The commit introduces that change, while reusing the same view classes
with minor modifications.
Merge branch 'split-county-experiments'

Conflicts:
	pombola/kenya/tests.py
MIT: update the social context text at Leah's request
Completely hide hidden people (don't even list them)

Previously we would still list people who were marked with hidden=True
and not link to their person page (which would 404 except for admins)
but this produced very unweildy lists of people on organisation or place
pages.

This commit changes this behaviour to not even list hidden people on
organisation or place pages.
KE: Add a script for hiding people on Mzalendo, as requested
MIT: correct a mispelling
MIT: set the Qualtrics survey ID for the new page
Refactor which people are included as related to a place

Fixes #1456
Restrict related positions to those which are "member".
Add a test suite to make sure we properly count people related to a place.

nb This test matches the current intent: as the code is written at the
moment, the count of people associated with the place contains every
person with a current position associated with this Place. This might
look confusing, since some of these people won't be findable through this
page, but that's probably another bug (either to change that displayed
count, or to include links to "other associated people").