ROVIO output image encoding

[svisschers]

I am trying to publish the visualizer output on a ROS topic, like in issue #35. However, I cannot determine what the encoding is of the OpenCV image data in mpFilter_->safe_.img_[i], and as such I get an encoding mismatch error in ROS.

[bloesch]

should be RGB, is created in ImgUpdate.hpp:
cvtColor(meas.aux().pyr_[i].imgs_[0], filterState.img_[i], CV_GRAY2RGB);