Add python bindings option

[ahoarau]

This just adds a python binding option that defaults to ON to be safe.
This is in part due to #1382

[rhaschke]

Could you please motivate the relation to #1382?
How do you expect users to change this option? Usually, building with catkin you cannot easily pass options to individual packages.

[ahoarau]

I'm using the c++ librviz for one of my projet. I had the exact same error as #1382 that stopped me from compiling anything on melodic. One way to pass the option :

catkin config --cmake-args -DBUILD_PYTHON_BINDINGS=OFF

But it applies for all the packages in the ws, it's true. Better than nothing :)
Copying the sources in the project that needs librviz and adding it with add_subdirectory(rviz) might work just as well and allow to pass the option to it individually.

[ahoarau]

So are there any issues on this one ?

[rhaschke]

The issue #1382 should be solved via ros-visualization/python_qt_binding#64.
Could you please verify? If so, I suggest to cancel this PR.

catkin config --cmake-args -DBUILD_PYTHON_BINDINGS=OFF

The option name is too generic. Better use something like RVIZ_PYTHON_BINDINGS.

[rhaschke]

Closing due to inactivity. Issue should be fixed as indicated in #1383 (comment)