Merge tag 'sparks-3.9.9' into develop

3.9.9
major README update/clarification/refresh.
Fix ubuntu powerline font installation on OSX.
Insert the docker installation documentation as a new task. Not yet implemented, but commands are here (tested on lafayette.licorn.org).
Fix symlinks creation in ~/ instead of ./
Mini-changes to docker docstring.
do not install nullmailer in LXC if postfix is already installed.
version bump
Merge branch 'release/3.9.10'

Conflicts:
	README.md