* Add item single click slot in labelDialog.py
In the original code, double clicking a list item will set the text property and automatically validate afterwards, with the label dialog window disappearing.
In this revised version, double click behavior is unchanged, while single click is added. When single clicking a list item, it will only set text in the QLineEdit. Users can change the text by clicking other items before validating themselves by clicking yes.
A line was commented out because there was an error. When a box was drawn
around an object and then saved, the file had a termination
".xml.xml" instead of just ".xml".
To divide the build failure problem to following:
1. current industrial_ci config is bad?
2. perception_pcl cannot be built on stretch, artful, and bionic?
The comment explains it in more detail. While we are at it,
fix the link in the README.rst to point to the right repository.
Signed-off-by: Chris Lalancette <clalancette@openrobotics.org>
```
% catkin lint .
pcl_ros: error: nodelet plugin file 'plugins/nodelet/libpcl_ros_features.xml' is not installed to ${CATKIN_PACKAGE_SHARE_DESTINATION}
pcl_ros: error: nodelet plugin file 'plugins/nodelet/libpcl_ros_filters.xml' is not installed to ${CATKIN_PACKAGE_SHARE_DESTINATION}
pcl_ros: error: nodelet plugin file 'plugins/nodelet/libpcl_ros_io.xml' is not installed to ${CATKIN_PACKAGE_SHARE_DESTINATION}
pcl_ros: error: nodelet plugin file 'plugins/nodelet/libpcl_ros_segmentation.xml' is not installed to ${CATKIN_PACKAGE_SHARE_DESTINATION}
pcl_ros: error: nodelet plugin file 'plugins/nodelet/libpcl_ros_surface.xml' is not installed to ${CATKIN_PACKAGE_SHARE_DESTINATION}
pcl_ros: error: unconfigured build_depend on 'message_filters'
catkin_lint: checked 1 packages and found 6 problems
catkin_lint: 40 notices have been ignored. Use -W2 to see them
```
