Content Location support

[SrivastavaPraveen]

I would like to add the content location support for Mime messages as per RFC https://tools.ietf.org/html/rfc2557#page-6. Please review my PR #81

[jstedfast]

You are probably happy with your fork of hpop + your Content-Location patch, but if you aren't, feel free to use MimeKit and MailKit which support Content-Location out of the box.

http://www.mimekit.net/docs/html/P_MimeKit_MimeEntity_ContentLocation.htm