Minor Description
If a file/ftp poller attempts to handle a message which isn't encoded in UTF-8 and which doesn't contain a PI to mention the correct encoding, the message exchange fails with an exception like "Line #273; Column #54; Invalid byte 2 of 2-byte UTF-8 sequence" when it encounters e.g. a Latin letter with diacritic.
We should add an optional 'encoding' attribute to the DefaultFileMarshaler to allow people to override the encoding when necessary.