snapshot versions noted by John
Fixed a couple of warnings.
Added a flag for HTML mime attachments that are probably the message body.
MIME text fixes.

Base 64-encoded text parts are no longer double-decoded. text/plain parts
that are attachments are treated as subdocuments.
Added a basic test for the MessageConverter.
Added mime types to ConvertedDocument.
XText tests are now deployed for reuse by other projects.