Stop including FileUtils.h in any header

This causes every piece of code which wants to use CFile or CDir to have to
include FileUtils.h. This causes quite some noise.

Signed-off-by: Uli Schlachter <psychon@znc.in>

WebModules.cpp

@@ -7,6 +7,7 @@
  */
 
 #include "WebModules.h"
+#include "FileUtils.h"
 #include "User.h"
 #include "znc.h"
 #include <sstream>