Country List on Front End

[adriancollier]

In Partnersites it might be clever to have the Country List only show the options for which there are projects present from that partner.

This would shorten the list and make it so that no matter which country you selected, you would always have at least one result.

We should do the same for Regions/Continents if we do this sort of filtering.

[KasperBrandt]

Merged in #518

[KasperBrandt]

Merged in #563

[KasperBrandt]

Test plan

GIVEN the Cordaid partnersite
WHEN the partnersite is opened
THEN the performance should be normal

GIVEN the UNDP partnersite
WHEN the partnersite is opened
THEN the performance should be normal

GIVEN a main page on RSR Pages
WHEN the page is loaded
THEN only the countries and continents belonging to the listed projects should be selectable in the filter

[rumca]

I've tested this on UAT by making multiple requests to both UNDP and Cordaid partnersites and I cant replicate the performance issues we experienced during the last attempted release.