v2.1.2

Permissions, groups (#3)

:warning: Breaking changes :warning: 

* Groups in Lab/Team outputs are now read and written as simple arrays of users.
  - In JSON format, users are represented by their URL (they're a nested object in HTML format)
  - You can update group members by submitting an array of urls/ids/objects with id property, mixing and matching as you see fit

* Simplify permissions
  - Permissions are now handled by user access levels, with a minimum level being set for each task (read, edit, delete).
  - User access levels are calculated for a user-resource pair and are: anonymous < registered < lab member < team member < team admin

* Specification generator container
  - Specification generation has moved to a docker-compose container `make_spec`