ol.source.ImageVector doesn't skip features

This fixes a bug [reported](https://groups.google.com/d/msgid/ol3-dev/7a208c83-d724-4e2f-ae2c-06e02423528a%40googlegroups.com?utm_medium=email&utm_source=footer) on the mailing list where multi-selection doesn't work when an image vector layer is used instead of a pure vector layer. The bug is that ol.source.ImageVector doesn' pass the skippedFeatureUids object to the replay group, preventing the select interaction to work properly.

Please review.