Bug Fix - Att::match

- Fixed bug in Att::match that causes blank dates to be interpreted
  as 12/31/1969, and therefore pass "xxx.before:" tests.
- Added the "cal" symlink trick to ChangeLog.
- Removed incorrect i18n tags from Config.cpp.
- Allowed .taskrc:confirmation=no to bypass Permission checking.

src/Att.cpp

@@ -560,7 +560,7 @@ bool Att::match (const Att& other) const
     {
       Date literal ((time_t)::atoi (mValue.c_str ()));
       Date variable ((time_t)::atoi (other.mValue.c_str ()));
-      if (! (variable < literal))
+      if (other.mValue == "" || ! (variable < literal))
         return false;
     }
     else if (which == "number")