fix: misaligned context items in ImageViewer

This is the announced workaround for the misaligned context items (#998). The issue of the workaround is a change in vtk version handling. 

tool/demo for testing: "pcl_pcd_select_object_plane" with input file: "trunk/test/milk_cartoon_all_small_clorox.pcd"

first test: vtk 5.8

before:
![imageviewer - vtk5 8 - before](https://cloud.githubusercontent.com/assets/4068805/5506562/afe32cf0-879b-11e4-80c5-7b25c958af28.jpg)
after:
![imageviewer - vtk5 8 - after](https://cloud.githubusercontent.com/assets/4068805/5506572/be0e4634-879b-11e4-8d21-ed89a81ce528.jpg)

second test: vtk 6.2, actual trunk
before:
![imageviewer - vtk6 2 - before](https://cloud.githubusercontent.com/assets/4068805/5506583/d546f792-879b-11e4-8183-9a7ae1473af0.jpg)
after:
![imageviewer - vtk6 2 - after](https://cloud.githubusercontent.com/assets/4068805/5506589/e270d7ee-879b-11e4-8064-fc2157bca5ce.jpg)