Fix extraction of Atom <content type="text"> and <content type="html">; we were failing to escape plaintext source data to HTML, and doing an extraneous double-deescape on HTML source resulting in breakage of notices containing text that looks like HTML. Only <content type="xhtml"> was working correctly previously.
Fixes for RSS2 content processing: we were failing to load <content:encoded> at all due to using wrong element name, and were applying an extraneous de-escape for <description> rather than the escaping that is required to turn plaintext into HTML. (Per spec, <description> must be plaintext.)
First steps to parsing RSS items as activities. RSS feeds don't seem
to have enough data to make good remote profiles, but this may work
with some "hints".
