[#665] Use DW::FormErrors for handling errors

* replaces @error_list with $errors; removes the code to print out
  errors on the page because this is handled automatically

* also adds DW::FormErrors->add_string, which lets you add a full string
  instead of the ml_key to the list of errors. This is useful for
  protocol errors and errors stored in variables (e.g., readonly error)
[#665] Stop using /update.bml and /editjournal.bml strings
[#665] Refactor DW::FormErrors to always have error.message

Instead of having to worry about whether we have the ml or the raw
message in the view, let's just let DW::FormErrors handle it. As far as
we're concerned we only need to worry about error.message (though the ml
and args are still available)
[#934] Show the edit entry again link unconditionally
[#665] Use DW::FormErrors for the warnings list
[#665] Convert the entry success page to foundation