Split into country specific repositories

[chrismytton]

As part of the transition project we want to split out two separate country-specific repositories. One for Kenya and one for South Africa.

This will mean branching the current code and for each country remove the code that isn't needed for that country to run.

There will be some duplication of the core code, but we think this is an OK tradeoff, as it will save a lot of time and keep more of the code in one place for future maintainers.

We think doing this in branches and then once we're happy with the branches pushing those to new repos is the way to go.

Two repos have been created already:

• https://github.com/mysociety/pombola-ke
• https://github.com/mysociety/pombola-za

There's also a draft pull request making a start on Kenya over at #2613

Follows on from #2603

[chrismytton]

I've renamed the repos to reflect the sites that they contain:

• pombola-ke ➡️ mzalendo
• pombola-za ➡️ peoples-assembly