Alfred3-interact

- There seems to be a race condition in `MatchMaker._init_member()`. Sometimes,
apparently a member has already been created, but the session ID is not available
in the database yet. We added a hotfix to try and make this problem less severe.
Now, `GroupMemberIO.load` will try to load the member data repeatedly, with
a one-second sleep in between tries for 15 seconds before aborting. In most cases,
this should give the database enough time to catch up.

- Set up continuous integration

- Added the parameter `shuffle_waiting_members` to `ParallelSpec`. If *True*,
groups will be composed after shuffling the list of waiting members.
If *False*, members who have been waiting for a longer time have a
higher priority (although their prioritization is not entirely deterministic).

- Fixed an issue that lead to problems with role assignment in parallel
groups.

- We refactored the matchmaking system to make it more robust, more
powerful, and easier to use.

- You can now *randomize* and *chain* group
creation through `alfred3_interact.MatchMaker.match_random` and
`alfred3_interact.MatchMaker.match_chain`. Both of these methods enable
you to take the special challenges of interactive experiments into
account. *Chaining* group creation is handy, for example when you want
to create groups of different sizes. Larger groups are harder to realize,
and thus you may wish to prioritize them: When possible, create a
large group. Only when large group creation fails, create the smaller
groups. Please refer to the documentation for more details.

- Matchmaking now requires the definition of "Group specs". These specs
currently come in three different flavours: `alfred3_interact.ParallelSpec`
for parallel (synchronous) groups, `alfred3_interact.SequentialSpec` for sequential
(asynchronous) groups, and `alfred3_interact.IndividualSpec` for
"groups" of size one. The latter allow you to include individual-sized
conditions in group experiments via `match_random` and `match_chain`.
You can use group specs to control the maximum number of groups that
should be created based on a specific spec via their parameter `nslots`.

- We changed the admin facilities to use the new admin mode introduced
in alfred3 v2.2.0. You can now add `alfred3_interact.MatchMakerActivation`
and `alfred3_interact.MatchMakerMonitoring` to your experiment
individually.

MatchMaker

- New method `MatchMaker.check_activation` allows you to check whether
the MatchMaker is activated at any time in an experiment. This
can be useful, if tha actual matching takes place at some later point
in an experiment: In this case, it is sensible to only allow
participants to progress, if they will actually be matched.

Chat

- New argument `room` for `ChatElement` and `Group.chat`. This argument
offers a convenient way to create distinct chat-rooms for the same
group of participants. Just enter a string as the group name; you may,
for instance, want to use a page name.