Merge branch 'ui/assmblies' into 'develop'

src/plainui/jinja2/plainui/assembly.html

src/plainui/jinja2/plainui/components/list_events.html

src/plainui/jinja2/plainui/components/list_rooms.html

src/plainui/static/plainui/img/rc3-assembly-event-01.png

src/plainui/static/plainui/img/rc3-assembly-event-02.png

src/plainui/static/plainui/img/rc3-assembly-event-03.png

src/plainui/static/plainui/img/rc3-assembly-event-04.png

src/plainui/static/plainui/img/rc3-assembly-event-05.png

src/plainui/static/plainui/img/rc3-assembly-event-06.png

src/plainui/static/plainui/img/rc3-assembly-event-07.png