Break up storyboard into multiple storyboards to improve compilation speed

[simontoens]

The storyboard takes annoyingly long to compile - breaking it up into multiple files would help to only compile what has actually changed. http://stackoverflow.com/questions/27432227/decreasing-storyboard-compiling-time-in-xcode-6

[MrStargazer]

In addition working concurrent on a project with such a large central file leads often to merge conflicts. With Simons solution those merge conflicts would rarely occur.