fix showing package changelog, version, filelist (bnc#868101)

by using an existing signal currentChanged(int)
instead of obsoleted currentChanged(QWidget *)
http://qt-project.org/doc/qt-5/qtabwidget.html#currentIndex-prop
Converted other currentChanged signals

from the dynamic SIGNAL syntag to the syntax checked at compile time.
changelog + version
Merge pull request #16 from mvidner/package-details

Fix showing package changelog, version, filelist (bnc#868101)