Silence some new gcc warnings.
Merge pull request #119 from ocommowi/bug-correct-generator

Correct bug in plugin generator for workspace type
Merge pull request #117 from papadop/gcc_4_8_warnings

Silence some new gcc warnings.
First try at switching to vtkImageView for thumbnails generation
Correct bug in vtkImageView
Add itkThumbnailGenerator, works for 3D and 4D scalar images
Cleaner thumbnail generator, propagate mirror to vtk meshes
Remove duplicated method
Remove warning in plugin generator