Remove the (apparently useless) statusbar

The statusbar doesn't seem to be used by the okular kpart, remove it. This saves some vertical space, and makes okularplugin another little bit better than kpartsplugin.
Before: http://s13.postimg.org/ne0s0qjjb/before.png
After: http://s13.postimg.org/86pdu4h2f/after.png