Progress reporting seems broken for ramp filter

[acoussat]

I noticed that, when running rtkramp -p . -r projection.mha -o /tmp/ramp.mha -v, the progress reporting output lacks the trailing newline, even though it should be accounted for. Playing a bit with progress commands made me realize that

• each thread of rtkFFTProjectionsConvolutionImageFilter::ThreadedGenerateData reports its own progress, from 0 to 100%, which is not the desired behavior;
• itk::EndEvent is never emitted.

It might be a problem linked to ITK, since ITK recently introduced commits that impact the threading model and progress reporting, such as InsightSoftwareConsortium/ITK@c8787b8ed8. It seems that updating filters can be required (InsightSoftwareConsortium/ITK@13fdc58236). But I'm not sure about this.

Unfortunately, I couldn't figure out (yet) a solution for RTK's ramp filter.