Changes regarding feature detection.
Added variant of ORB that can be adapted
Fiddled with SiftGPU parameters to find more keypoints
Small changes
Removed adapting nn_ratio
minor code change
changed default use_feature_min_depth to false
Fix of a subtle bug.

For ORB the sub-pixel keypoint coordinates where sometimes so
close to an integer (e.g., 39.999976) that, seldomly when checking
for NaN after descriptor extraction, a different pixel would be accessed
than before extraction.
Stand der Dinge für den Wochenend evaluationslauf
Bugfixes regarding features and reordered feature code
Changes Regarding the evaluation of the detector type

Instead of comparing the max_keypoints, the adjuster
now computes a minimum of <max_keypoints> keypoints
and then the Node class cuts it down. Thus both,
the regular and the adjusted detector will detect
more keypoints and cut it down to <max_keypoints>.
Except if the regular detector finds less...
Removing debug messages
Fixed subsampling of clouds for display

cloud frames are now dynamically subsampled when updating due to
new data.
fix for SIFT Adjuster
bugfix for EMM with subsampled clouds
Merge branch 'hydro' into visual_odometry
Adapted visual odometry launchfile to change in feature detection