Update to KA Lite 0.17

[benjaoming]

This could be a good start to the Django migration for the central server:

1. Upgrade the git sub module
2. Adjust the PYTHON_PATH
3. Deploy on Globe?

https://github.com/fle-internal/ka-lite-central/blob/develop/centralserver/manage.py#L23

[benjaoming]

Dropping some notes on the current submodule:

It's pointed to a118a2d42c30e5df99e71d5923fb294e222eacbf - a commit that isn't part of central-master branch.

It was merged to central-develop which seems to have been deleted. See for instance: learningequality/ka-lite#5095

I think the immediate action to take will be to just push the head of a118a2d42c30e5df99e71d5923fb294e222eacbf straight to central-master so there's a branch tracking what's deployed to the Central server once again.

After that, work can start to get rid of the submodule.

[benjaoming]

I've deleted central-master from ka-lite to avoid further confusion. It's replaced by central-develop which points to the deployed commit has, which is also tagged. Both the tag and the branch are necessary for submodules to actually work.

[benjaoming]

I'm now merging current 0.16.x into central-develop. It seems that python-packages/securesync/api_client.py had a change that didn't go into 0.16.x, so good to be mindful of.

[benjaoming]

It seems we need to get learningequality/ka-lite@cde79ba in the branch to make it work, however the removed nested submodule has been relocated so it can't be cherry picked.

[benjaoming]

This is fixed now and deployed and love 🎉

CC: @jamalex @aronasorman

[benjaoming]

The main changes were here: #307