Merge IDOC code to develop

I would like to merge this code immediately, without code review, to develop.
* This code is in production.  It has extensive testing and has been worked on by a number of people.
* This code needs to become public on our team, and used by all--in order to test further.
* All new merges to release-0.10 must also be merged here.  Those who created the pull requests must make sure things merge here.

By doing this, we're taking a critical step in bringing these two codebases back together.  We need to figure out a process of how to review this code for the long-term, but for the short-term, we need to be at least having people merge their code into this codebase, so that they become aware of differences, and develop on here when relevant.

This code contains the following changes:
* Changes to the update procedures (in-progress): videos, software, and subtitles
* New download / install process (with zone information), including generating zones on distributed servers, ZoneInvitations, and ChainOfTrust objects
* An earlier version of @arnaudbenard 's `frontend` branch