Option to skip No Mandate exceptions

[johannessen]

Plain out refusing to work with debit files when just a single mandate is missing isn't very helpful. We should offer to skip past such exceptions rather than bailing out immediately.

Workaround 1: Do a "dry run" before the real thing. Such errors will then surface early and you'll avoid the issue altogether.

Workaround 2: Manually edit the debit file in any text editor to remove the offending row. Excel should really work too, but is untested and therefore unsupported at this time.

(This was issue #161 in the old THAWsoftware tracker.)