Improved the spacing between sections and subscetions by using \addvspace instead of \vspace

KNOWN_BUGS

@@ -3,3 +3,8 @@
 - Moderncv produces an error ("lonely \item--perhaps a missing list environment")
   when used with bibentry, through the output is actually correct. Amongst other,
   this causes compilation by LyX to stop.
+- The space after a cventry gets eaten up when the last argument contains a nested
+  itemize environment. An ugly hack and uncomplete solution was implemented by
+  including a \strut in every item label, but this doesn't solve the problem for
+  multi-line items. Ideally, the strut should end the item, but there seem to be
+  no way to do this.