Quickfix: Expand columns to available space in landscape mode.

I noticed that the schedule columns **do not expand in landscape mode** if there are just two or three as shown in the screenshot.

![Schedule columns](https://cloud.githubusercontent.com/assets/144518/5057697/94cb90a0-6cd0-11e4-8dd9-dbf481205df0.png)

This can be tested if you build the *fiffkon14* flavor at commit [cf93c](https://github.com/johnjohndoe/CampFahrplan/commit/cf93ccb0322f5e4176fc13fffee192ff8a8e3213).
I digged into the plucks of the view and came up with the following **dirty quickfix**. Can we please find a nicer solution before this is merged into upstream?