Document outstanding issue with dataTable, commandSortHeader and input components

Issue MYFACES-228 describes a problem with table sorting when the table has input components.
That issue has been marked as closed even though the original problem was never resolved.

There is a partial workaround: set immediate=false on the commandSortHeader. Attached is a patch
to at least document that this is necessary for commandSortHeader.

Ideally the original bug would also be reopened, or this entry used as a continuation of that issue, as the problem isn't properly resolved.