StreamLinesRepresentation: Various fixes and improvements.
1/ Address a bug when using thick lines (width>1) with GL 3.2 core profile. With this profile (used on some systems), glWidthLine() does not have effect and generate an error: one must process line thickness manually. A striped version of the geomtry shader of the OpenGLPolyDataMapper has been reproduced here.
2/ Change the blending equation to support any background color.
3/ Support for actor/user transform.
4/ Add a new "Animate" option to turn the animation ON/OFF.
5/ Tests are also introduced thanks to a new optiow "NumberOfAnimationSteps" which perform a single rendering pass with the given number of steps and then stop updating.