hot fix: re-enable csv download and fix csv download name.
group of groups are identified by flag now rather than by an arbitrary number of members.

Please mark a group as group of groups by setting:

     my_group.group_of_groups = true

You can check by:

     my_group.group_of_groups?

trello: https://trello.com/c/iGdAIonm/655-alle-verstorbenen-wingolfiten
vertical nav: show corporation title in collection groups in the vertical navigation.

For example: Let all corporations have a status group 'foo'. Then, let another group,
called collection group, e.g. 'all foos', have all foo groups as children.
Now, they don't show as 'foo' in the vertical nav when viewing the collection group,
but they show up as 'foo (corporation name)'.
When viewing within the context of the corporation, they show up as 'foo' as usual.

Trello: https://trello.com/c/iGdAIonm/655-alle-verstorbenen-wingolfiten
groups#show: order group members in descending order by date of joining the group, i.e. last joined members first.
fixing caching task.
caching: reset dependent caches when adding an officer.
root#index: show current member development boxes in the right column on the start page.
recalculate validity ranges during the cache:all task.

This corrects wrong membership validity ranges for indirect memberships
on a regular basis.
adding cache for latest members boxes.
quick fix for latest members boxes: to get the latest members from the cached array, use the #first(3) method rather than #last(3), since the array is sorted DESC.
groups#show: for corporation member lists: do not use the membership objects of aktivitas and philisterschaft, but the memberships in the corporation.

This issue has been the reason for wrong dates in corporation member lists.
fixing box header layout.
remove validity range recalculation from caching task.

* This is no caching.
* This takes too long.
* 'save' was missing.
* This fills the RAM.
* There was no checking if this was needed. Simply all memberships were recalculated.
fixing an issue where admins of a group could not edit the group's profile fields.
fixing issue with 'rake cache:groups'.
User: fixing nested caching calls in User#title.
adding who-is-online display (last_seen_activities).

User.last_seen_activities
User.update_last_seen_activity('is eating lunch', lunch_object)
User.update_last_seen_activity(nil)  # on logout

LastSeenActivity.current  # 5 mins

trello: https://trello.com/c/51DTx3aY/659-wer-ist-online-anzeige
Aktivmeldungsbutton: Der Button wird nun in der Aktivmeldungsbox auf der Startseite angezeigt, nicht mehr unter dem Menü. Im Notfall ist er auch im Dropdown 'Hinzufügen' zu finden, das eigentlich für Structureables gedacht ist.

Der Platz unter dem Menü ist zu voll geworden. Außerdem hat sich der Platz in der Box der Aktivmeldungen thematisch angeboten.
who-is-online view: keep alive if the user hits 'reload'.
Aktivmeldungsbutton: fixing spec.