Fix ImageViewer in VTK 6.1
Merge pull request #1017 from VictorLamoine/vtk6_fixes

Fix ImageViewer in VTK 6.1
Add tcp_open_
Add missing const qualifiers
Update doc & formatting
Add grabSingleCloud
Move camera_ to public
Rework transformation functions
Add extrinsic calibration functions
Add image capture callback
Eigen fixes