changed all empty-string instances ("") to QString().
Changed QString function arguments to "const QString&"

The first item was done in all code directories, but the second has only 
been done in the main kstars directory.  Need to propagate changes to 
tools, widgets, and skycomponents directories.

CCMAIL: kstars-devel@kde.org


svn path=/trunk/KDE/kdeedu/kstars/; revision=509265