Fixes for setup.py under Ubuntu 18.04

[Tuebel]

Hey,

I had some issues with the pip version of python-pcl since it seems to depend on pcl 1.7 (pretty much the same as here #317).
One advice was to install it from source via python3 setup.py install, which failed for me. This pull request contains the fixes I have made to build this lib:

• Ubuntu 18.04 uses pcl v1.8 with vtk v6.3 -> changed vtk_version from 7.0 to 6.3
• linking vtk 6.3 yielded some linker errors. Removing the missing libraries from the list fixed the issues for me.

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This change is 

[mpitropov]

I was able to install on Ubuntu 18.04 using this branch.

[dogghou]

Hey,

I had some issues with the pip version of python-pcl since it seems to depend on pcl 1.7 (pretty much the same as here #317).
One advice was to install it from source via python3 setup.py install, which failed for me. This pull request contains the fixes I have made to build this lib:

• Ubuntu 18.04 uses pcl v1.8 with vtk v6.3 -> changed vtk_version from 7.0 to 6.3
• linking vtk 6.3 yielded some linker errors. Removing the missing libraries from the list fixed the issues for me.

This change is 

My environment: agx-xavier + ubuntu18.04 + vtk6.3 + python-pcl
I use this way to install the python-pcl successfully. But when i use pcl_visualization to visualize the points cloud, it aborted.
And i notice that you add pcl/pcl_visualization.cpp in the file named .gitignore, do u mean the visualization can not work.

When i test, the errors :
ERROR: In /build/vtk6-5rzKol/vtk6-6.3.0+dfsg1/Rendering/OpenGL/vtkXOpenGLRenderWindow.cxx, line 394
vtkXOpenGLRenderWindow (0x20813810): Could not find a decent visual

ERROR: In /build/vtk6-5rzKol/vtk6-6.3.0+dfsg1/Rendering/OpenGL/vtkXOpenGLRenderWindow.cxx, line 394
vtkXOpenGLRenderWindow (0x20813810): Could not find a decent visual

ERROR: In /build/vtk6-5rzKol/vtk6-6.3.0+dfsg1/Rendering/OpenGL/vtkXOpenGLRenderWindow.cxx, line 394
vtkXOpenGLRenderWindow (0x20813810): Could not find a decent visual

ERROR: In /build/vtk6-5rzKol/vtk6-6.3.0+dfsg1/Rendering/OpenGL/vtkXOpenGLRenderWindow.cxx, line 633
vtkXOpenGLRenderWindow (0x20813810): Cannot create GLX context. Aborting.

Aborted