activity log for all instances of broadcasts

delete actions for broadcast and broadcast repeats

to keep activity entries in broadcast instance activity stream

init activity stream with actstream from
https://django-activity-stream.readthedocs.io/

own app "activity" as hack to register user model

inital default views at /manage/activity/ , to be customised

Stammsendeinhalte (RadioProgramRegularItem) einer Sendereihe
(RadioProgram) zu einer Sendung (Broadcast) hinzufügen, ändern, löschen

Stammsendeinhalte (RadioProgramRegularItem) können aktuell im
Adminbereich erstellt werden

Stammsendeinhalte (BroadcastItem:regular) werden zu den Sendungen
(Broadcast) bei deren Instanziierung erstellt anhand der Stamminhalte
(BroadcastTemplateRegularItem) in der Sendungsvorlage
(BroadcastTemplate)

Vorhandene Stammelemente (RadioProgramRegularItem) wie Nachrichten,
Wetter, Sport etc. einer Sendereihe (RadioProgram) zu einer
Sendungsvorlage (BroadcastcastTemplate) hinzufügen, bearbeiten, löschen.

Stammelemente (RadioProgramRegularItem) können derzeit vorab nur über
Adminseite einer Sendereihe (RadioProgram) hinzugefügt werden

We need these to easily display the upcoming broadcasts based on the
current time.

We usually want to display upcoming broadcasts, so it’s nice if the
default order is ascending.

daten modell und erste views, um generische programmpunkte wie
nachrichten, frühsport etc in den sendeablaufplan aufzunehmen sowie
zuvor einem broadcast template zuzuordnen

This reverts commit 948b8fcf.

This is necessary to make a new merge of the feature branch 100-*
possible

This also changes the choices field, as actual code references like the
one created by __members__.items() will break migrations in the future,
when the code changes.

Browser clients have limited power over the response, specifically the
name of the file in a response. The anchor (a) element had support for
the download attribute for quite some time but is only applied for
downloads from the same origin. As clients should be able to consume the
the lohrothek api from other origins, the filename should be
configurable through the request.

Without these headers media files like images can be loaded by the
browsers DOM but not be examined in JavaScript. This is usually not a
problem but frontends might want to analyze images or other dynamic
content. For instance thekno will look at the overall brightness of an
image to determine the impact of filter effects and will adapt it
accordingly.

we need this value to properly address tracks in the queue.

Revert "Merge branch '100-quick-create-reports'"

See merge request !3