Unrecognized inline attachments

[Feliix42]

As pointed out in offline discussions, detach does not recognise some attachments from Apple Mail because it inlines them.

This produces something like the following:

--Apple-Mail=_FF297101-ED64-4306-A433-DA2DB722FFB0
Content-Transfer-Encoding: base64
Content-Disposition: inline;
	filename=171214_Kachel_Campus_Weihnachten.png
Content-Type: image/png;
	name="171214_Kachel_Campus_Weihnachten.png"
Content-Id: <[...]@ifsr.de>

[Base64-Blob]

As opposed to normal attachments, the Content-Disposition field is set to inline, which is unfortunate because detach bases its recognition on this field.

Maybe we could extend the attachment criteria to include any message parts that are inline, but also of type application/pdf, image/png, image/jpg etc. This would be a kind of hacky solution but better than nothing. What do you think, @cirdeirf?

[cirdeirf]

This seems to be a reasonable approach to deal with this problem. One could consider checking wether the used client is indeed Apple-Mail before extending the attachment criteria but explicitly checking for these types every time probably does not do any harm anyway.