Refactoring the spatial object node

Methods were implement multiple times because the type varied. Using
template functions, we can factorize those methods.
Refactor the creation of display nodes for spatial object

It was done both in the logic the node two different ways. Instead, we
move all the display node creation in the node. We also enable tubes by
default.

Note that at this point, there are visualization issues still. The tube
aren't visible until we click on the node in the spatial object widget.
This will be addressed in the next commit.
Refactor the display pipeline
Show the tubes on by default.

We already turned the display of the tube to visible. We also need to
set the default scalar name array for them. Otherwise such array does not
exist and they're not displayed.
Merge pull request #370 from KitwareMedical/TubeVisibleByDefault

Tube visible by default