Roi analyser

Problem noticed during Montpellier workshop.
To test the PR.
 * Need to reduce the default memory allocated to insight so it is easier to reproduce (64M)
 * Open an image with several z-section or timepoints.
 * Open the measurement tool
 * Draw a rectangle and propagate the shape across few z or t
 * Go to "Intensity Results Tab"
 * After a while, a dialog indicating than an error occurred will pop up.
 * Click OK and check that all the controls do not stay greyed out.