Fix 4.0.0, which does not work on both Melodic/Noetic (#43)

• use LooseVersion(wx.__version__) to support old Melodic (wxPython 3.0)

• typos

• more deprecated functions to test on melodic

• why wouldn't this work with python3 ?

• add missing dependency on cv_bridge

• update use of deprecated functions

• update pckage.xml based on https://github.com/ros-visualization/executive_smach_visualization/pull/39

• use catkin_install_python to automatically set /usr/bin/env python3 for noetic, but need to remove smach_viewer/lib/smach_viewer from sys.path

• xdot/wxxdot.py: intentionally uses from xdot, instead of from .xdot, because we want to use local xdot for Pytohn2 and sytem xdot for Python3

• Revert "apply 2to3 -w -f import *" This reverts commit 4cbd2ab0d16d4123e9227bf6b9e627bd4bd8ea7f.

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Contributors: Kei Okada, Mikael Arguedas

Allow launching from a launch file, use rospy.myargv() to remove ROS remapping arguments (#16) * Use rospy.myargv() to remove ROS remapping arguments Required to allow launching from a launch file, otherwise get errors of the type: ```

usage: smach_viewer.py [-h] [-f] smach_viewer.py: error: unrecognized arguments: __name:=smach_viewer

```

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• Solved 'Cannot start smach_viewer.py in launch file' problem #17

Contributors: Kartik Mohta