Allow all attributes on 'span' elements for tinymce content. This fixes: LP #1105224 Posts with Embedded Kaltura Videos Lose Content on Edit.
It appears that tinymce cleans tags more agressively than before.
The SPAN tags need to have different non-standard attributes
because both the embedmedia and the kaltura plugin uses this
for an internal processing step. Earlier tinymce versions did
not cause any trouble with that. To fix this to work in the
current setup, we need to allow all atributes to SPAN tags.
update changelog