What changes will be made and why they would make a better Orfeo ToolBox?

In OTB we have a lot of filter that can be used on image or vector image. Those filters have the same purpose but not the same name and sometimes not event the same convention.
What can be done is using template meta-prgramming to try to unify those filters (as for the ClampImageFilter using the convert type functor) hence decreasing the number of class to maintain.

High level description

The following filters can be merged :

• ShiftScaleVectorImageFilter & ShiftScaleImageAdaptor (Warning : not the same convention)
• StreamingStatisticsVectorImageFilter & StreamingStatisticsImageFilter (related filter : VectorImageToMatrixImageFilter, StreamingMinMaxVectorImageFilter, StreamingMinMaxImageFilter )
• ExtractROI & MultiChannelExtractROI & MultiToMonoChannelExtractROI

The idea is to make it transparent for coders : FilterType<ImageType> and FilterType<VectorImageType> will have the same behavior and functionnality but will adapt depending on the template parameter.

Risks and benefits

No particular risks.
Benefits : less classes to maintain, less copied/pasted classes, less bugs (hopefully...)!