Fix for Bug 7194 - OPAC detail and recent comments pages corrections for XHTML validity

Fix for Bug 7194 - OPAC detail and recent comments pages corrections for XHTML validity

- Adding html filter to subtitle output to correct unescaped ampersands
- Adding missing alt attributes to libravatar output
- Removing unecessary markup  from comments page

Bonus: Adding html_break filter to output of comments to preserve line breaks
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>
(cherry picked from commit fe9312a1240e58a04b0cd0c322d46c34a4b51891)

Signed-off-by: Chris Nighswonger <chris.nighswonger@gmail.com>