Add keywords to .desktop entry; fix.

Author: kpeeters

config/cadabra2-gtk.desktop

@@ -8,7 +8,7 @@ Icon=cadabra2-gtk
 Categories=Math;Science;Education;
 Exec=cadabra2-gtk %f
 Terminal=false
-Keywords="computer algebra", "physics", "mathematics"
+Keywords="Computer Algebra";Physics;Mathematics
 MimeType=application/cadabra;application/x-cadabra;