NEW : display vectors

- NEW : When a vtk file contains attributes with 3 components, it is able to display them when the attribute is selected.
- ENH : access to the mesh actor has been changed using the first actor of the renderer window
- ENH : a lot of actors access were actually useless : it was quicker to access using m_meshList instead od m_windowList

Next to come : customization of the vectors displayed
NEW : modify vectors scale manually

- NEW : we used a scrollbar to adapt the vectors scale between 0 and 3 with a 0.1 step
- ENH : modifications of the GUI in the colormap optionsto optimize the arrows usage
NEW : mesh opacity

- NEW : a slider helps you changing the surface opacity to be able to see the vectors more easily
- ENH : deletion of useless librairies and setting in SHapePopulationBase
ENH : add attribute dimension in the data table

- The attribute/ranges table also displays the dimension of the attribute
BUG : move glyph actor on reposition

- BUG : when selecting CEnter position, only the surface actor was translated.
- CLEAN : deleted useless lines commented for renderallselection
NEW GUI + BUG delete / label colors

- NEW : the GUI is optimized in the colormap box to be able to modify vectors features. The checkbox "dislpay vectors" and the option " Vectors Density" are not implemented yet.

- BUG : erase the m_glyphList when deleting windows

- BUG : modify actor id during the label color modification (add 1 because of the new glyph actor)
BUG : labelColor saved like background colors

- BUG : just like the selected and unselected background color, the label color is now stored in a 3D double array in SHapePopulationBase
- ENH : moved the functions dealing with vtk objects in ShapePopulationBAse instead of ShapePopulationQT (textColor, vectors sliders)
NEW : vectors magnitude displayed + big update

- NEW : vector display
- NEW : vector vector density
- NEW : creation of the magnitude attribute for each vector attribute, to display the magnitude attribute in the scalars. Using vtkPVPostFilter from Paraview to get this attribute from the vectors.
BUG : includes from VTK install

- BUG : the library vtkArrayIteratorIncludes.h was not installed in VTK but present in VTK build during the superbuild. We just put its content in vtkPVPostFilter.cxx since it was only including other librairies.

- BUG : correcting the windows bug of arrows for hide/show toolbox, by displaying ^ and v instead if WIN32
NEW : display colorbar

You can use the checkbox on the right of the colorbar to chose to hide or display the colorbar in the renderWindows.
CLEAN : comment lines and modify GUI

Mostly useless, but still modified it.
NEW : prepared for Slicer Extension

- in CMakeList.txt : if built as a SLicer Extension, set EXTENTION_VARIABLES, set SUPERBUILD to OFF, and look for SLICER and SLICER_EXTENSION_PACK
- in src/CMakeList.txt : if built as a Slicer Extension, do not redefine install destinations
- in vtkPVPostFilter : got rid of vtkStrString and used std::string instead