first attempt to implement section headers in news list
added attribute 'simplifiedDate' in news model for usage as sort descriptor
added icon for 'all sources', replaced selection indication by translucency in source navigation bar, replaced read indicator view in news and event cells
refined map tiling
Merge branch 'Maps' into News
Merge branch 'Mensa' into News
tweaked date sectioning
tweaked date periods (again)
tweaked sectioning (once more)
Bearbeitung von SearchViewController;
Merge remote-tracking branch 'origin/Maps' into Maps
several layout adjustments
minor layout tweaks
fixed auto layout issue
implemented basic search setup
Merge branch 'Mensa' into develop
Merge branch 'News' into develop
Merge branch 'Maps' into develop