Pull fixes and enhancements from downstream forks

[pangelo]

Over the lifetime of this project there have been several fixes and enhancements made by downstream forks that might be worthwhile to pull into this repository.

Here's how to help out:

• look for a downstream fork that has made changes to this codebase
• go over the fork's commits and check if the changes made are still valid upstream
• create a branch from "altlab/liquid-feedback-docker" at the revision the downstream commits are based on
• cherry-pick the downstream commits (to maintain original authorship)
• rebase to upstream
• test it, making any necessary changes to get it working
• make a pull request

[pangelo]

likely candidates:

• mildred/liquid-feedback-docker: updated build process to support newer versions of LF, likely superseded by 48ed0b0, but there might be some bits worth porting over.
• DarkGigaByte/liquid-feedback-docker: forked from an older version, has many changes, some probably obsolete by now. This is the version with more downstream forks.