Image Sequencer examples/tests are out of date.

The 'images.cnd' file falsify comments that the 'image:metadata' is a mixin type.

It would be good to have this removed (the comment) or perhaps support a mixin 'image:metadata' type to allow for metadata to deocorate 'nt:file' or 'nt:resource' nodes.

Not realizing that this was the case was causing the exemplary pathExpression configuration `["default://(*.(gif|png|pict|jpg))/jcr:content[@jcr:data]"]` to fail (obviously when using nt:file objects with names fitting the regex).