Modify Ogg handler to keep metadata comments in utf8

Previously it was converting to ISO 8859-1.

Change-Id: Id6551dfc3ad199696cce2742813bb521a314de38
Output ogg metadata on image description page.

As an aside, this was one of the primary goals of my 2010
gsoc project. I'm only 4 years late.

This just does basic support (throws all the metadata of each
type together), nothing fancy like separating out metadata by
different streams is attempted.

Bug: 47487
Change-Id: I2adacf4199a4da559f8225fd9f37cbcc3eac21ce