image support in XMPP clients

revision 836c56e3c5f631fda8a9fa3e0525ddfbb897428a

Swift <http://swift.im/>:: 2015-11-13: > It doesn't render the html-im part at all. It just renders the plain body.
`Psi <http://psi-im.org/>:: System Message: WARNING/2 (<stdin>, line 4); backlink
Inline interpreted text or phrase reference start-string without end-string.

2015-11: Only images with data: src attributes are rendered, no external ones