Added Optimize ABC action (remove unused items) - available through ABC Explorer

Fixed Outputstreams position calculation (ABCOutputStream, ...)

libsrc/ffdec_lib/src/com/jpexs/helpers/NulStream.java

@@ -16,6 +16,7 @@
  */
 package com.jpexs.helpers;
 
+import java.io.IOException;
 import java.io.OutputStream;
 
 /**
@@ -26,5 +27,5 @@ public class NulStream extends OutputStream {
 
     @Override
     public void write(int i) {
-    }
+    }   
 }