Updates for MAVLab course 2019

[tomvand]

Updates:

• OpenCV from version 3.2.0 to 3.4.5. Also added contrib features.
• Restructured makefile to compile multiple targets at once. OpenCV is now compiled for both the Bebop and the host PC, so that the exact same version can also be used in NPS/Gazebo.
• Builds opencv_world instead of separate libraries for easier linking.

[tomvand]

Thanks! Merged.