Figure out what to do with user-added CAs now that we target API 24
See the discussion started by @relan on !352 (closed).
Before releasing 0.101, we should do one of:
- Decide to not do anything, breaking backwards compatibility.
- Add the lines to the manifest to allow user CAs again.
We can also release 0.101 breaking backwards compatibility, and see if anyone complains. If they do, then we can fix it on master and backport for 0.101.1.