[media] DocBook media: update copyright/version numbers

- Update the copyright year to 2015 in media_api.tmpl.
- Main version number of the spec updated to 4.4.
- Version 3.21 was used for one changelog, this should be 4.1.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>