Code Cleanup

- Renamed files task.h -> main.h, task.cpp -> main.cpp.  This is to
  prepare for the next rename, which addresses the OpenBSD bug.
- Removed utf8.h, utf8.cpp from Makefile.am, which were inadvertantly
  added.

src/edit.cpp

@@ -38,7 +38,7 @@
 #include "Date.h"
 #include "text.h"
 #include "util.h"
-#include "task.h"
+#include "main.h"
 
 extern Context context;